So...as a huge highlander fan (I do not subscribe to many fandoms... Highlander and Castlevania and a few others...)
Highlander 2:
Big "lore" mistake of 2: Immortals come from the planet zeist - this is NOT a re-telling, this happens after HL1, Connor won the prize, used his super brain to make the shield and saved humanity... but well he got emo and a company took over and now he needs his old buddy Sean Connery to be yelled at to resurrect himself, then to come interrupt an opera and then stop a ceiling fan for him to then pess the open door button so we can see, oh look the earth healed itself (contrary to its own ozone doom message)
Okay, so they get tons of flack for prisoner alien immortals or whatever, so they made a new edit and take out all the crap about zeist, and...change it..to..the past? or something and now they are just random time travelers...it makes no sense it is just a better cut because no one says the planet zeist. Either way, it pisses all over the lore. It has a big change in tone because its like post-apocaliptic neo future type sci fi... but that can be done - look at the Highlander Anime (not animation)
Yet, even with edits, it butches the core lore.
Also a huge Highlander guy. Not many things I have "fandom" for: Pretty much just Highlander, Terminator, and the show 24, in that order.
Never seen the Renegade Cut of HL2. I have it (thanks to getting a series DVD set). It's much easier to find than the theatrical version, which I've only been able to find on Youtube. Can't say much about the Renegade Cut until I see it. Original HL2 is full of issues, from Planet Zeist to just reviving Ramirez for no reason and giving him magical electric powers. It was cool to see Ramirez in the modern era though, not knowing what an airplane was. Wonder what kind of reaction he had to finding out about toilets.
Highlander End Game:
Okay... so, it starts where the first show episode started.. Connor and Duncan together - the show retconns HL1 to just /starting/ "The Gathering" - they mention Connors battle with The Kurgan etc. by the watches. The show adds tons of lore expansion based off of mostly HL1, but some 3. The show is generally regarded as really good, and it is - in terms of "lore" they do not do anything odd or crazy or anything that does not make sense within the universe of Highlander - even the "dark quickening" near the end, fits- it was just restricted by time and money (more on that....soon)
So where does end game poop all over established lore like HL2? Sanctuary... The fact that the watcher's immortal Sanctuary nap time pod place is NOT holy ground makes negative 500% sense - it holds no logic that the watches would make it NOT on holy ground and it holds zero logic that any immortal would sign up to enter the sanctuary.
Secondary is Dunan's woman issues, there was so much they could have done better on this, but it is not really as bad or lore breaking as the sanctuary issue - but it also plays off much of the series- it kind of just is like, 1st episode of the series...meh...stuff...nothing really matters... endgame! Rather than using all of the stuff they had in terms of characters, plots to expand upon etc.
So... for the creators to just somehow GLOSS OVER the ENTIRE holy ground thing... yeah, up there with zeist.
Highlander: The Series is where it's at, and the is IMO best part of the Highlander mythology. Yeah, the first movie is great, but if you stacked it up against the various movie-length multi-episode arcs in the show, I'd say HL1 would only be like the 2nd or 3rd best out of the group. The show has some extremely good arcs in it. The Kalas arc (five episodes) that introduces Methos is probably the show's highest point and culminates with the Duncan/Kalas fight on top of the Eiffel Tower that most people probably think of when they think of the show. Duncan losing to Kalas in the opera house was also a pretty rad moment, since I could probably count his lost (and almost-lost) fights in the show on one hand. Kalas, Kronos, Grayson, Otavio Consone, Brian Cullen. Yep, one hand.
One of the reasons the show is so good is, like you said, they stick within the mythology of HL1 very closely and don't do anything crazy or wack. A woman who can see the future is about as far off the reservation as it ever gets. They do retcon Connor being the last immortal (by necessity) and have Connor vs Kurgan just be a huge clash of immortals that kicked off the Gathering, like you said. The whole Gathering concept was pretty much abandoned after season 1 though and it went from "only a certain amount of us are left and there can be only one" to "there are lots of us left and more are born all the time and there can be only one but lol that's probably not happening"
Oh yeah, Endgame... the main problem with it I totally agree with you on. The Sanctuary was a useless fucking concept if it wasn't consecrated holy ground. A place where immortals could sleep safely in perpetuity through the eons was an interesting idea, especially for those who were tired of life like Connor. If it wasn't holy ground, then WTF?
Except I'm pretty sure it WAS holy ground and the movie was saying Jacob Kell was just SO BAD that he could just ignore the holy ground rule and kill there regardless. He does refer to it as "the so-called sanctuary" which makes me wonder if it wasn't actually blessed and he was aware of this fact somehow.
The other bad thing about Endgame was that Faith was just this out-of-nowhere woman from Duncan's past. Would have worked better to have Amanda from the series in this role, under Kell's influence for whatever reason. They also said that Duncan and Faith had been married for one day, which directly contradicted the show's repeated assertions that he had never been married and, according to the psychic woman, never would be.
Highlander: The Source
Okay, here me out... and no I do not think its a better /movie/ than the others... but I kinda feel it gets a little bit /too/ much hate.
The lore of the movies and show is followed, the movie deals with things hinted at, and now new and expanded elements of the mythos - such as the guardian and the source.
It brings back and uses characters - poorly, but they tried as with endgame, ehhh.
So I give this in general to say, 2 and EG butchered key things. TS moved on and expanded upon things...just...really...really...bad... Honestly the first like 30 min of The Source is fairly well done, then it gets to find a new BMW SUV in the woods dumb. The dock fight scene is good, the asian dude fighting the guardian in the opening scene is good (if you edit the "animal" type shots away from the guardian) etc.
The thing about this is... HL2 at least feels like a Highlander movie, even if it butchers its own lore and makes no sense. It's got the Highlander vibe, overconfident immortals, sword fights. The Source has none of that, and no vibe. The Source feels like a rejected horror movie script that someone repurposed into a Highlander movie. Duncan loses his sword almost immediately, loses his immortality by the halfway point, and the rest is him and a bunch of randos running away from
cannibal hordes and a monster with inhuman speed leaping between trees like the predator.
It has nothing to do with Highlander. Matter of fact I'd bet money it's a rejected horror script.
Anna also comes out of nowhere as the latest "love of Duncan's life" we've never heard of before. Would have made a lot more sense if this had been Anne from the show. Still doesn't make sense because wasn't he with Faith after the last movie (who should have been Amanda)? Jesus Christ... this series can be bad.
So... The dark quickening, -spoilers for the series- the season change from when the dark quickening took over duncan, killed richie and ended that season- the entire intent was to time jump ahead to a post-apocalyptic type setting. Duncan was to be in his dark quickening coma state for a chunk of time- during this, the evil presence that he "fought and overcame" in the show- did not happen, it was released outward to the world and took over / possessed a bunch of immortals, making good ones bad and bad ones very bad- immortals "came out" to the world and took over etc- basically the end times.
Duncan was then to have his quickening / essence return to the source where he was filled with "the good" side and sent out then reborn (Gandalf the white!) to fight the bad guys and purge the evil essences / send them back to the source for destruction or repression or collecting - whatever. BUT all that would have cost WAY TOO MUCH MONEY.
So, when The Source got green-lit, it had many many of those elements, but for once, trying to keep a semblance of continuation from what already existed they changed some stuff. I will say the source suffers from what many B-movies do- trying to do too many good ideas, in one film because "we wont get another! and this HAS to BE IT! for even a chance at another! So ALL THE IDEAS!!!" - the four horsemen that are only in the vision / backflash, the elder guy, the cannibals in the woods, becomeing mortal, all of these could-be-good threads that are there then just moved on from.
So... if I was to compare the source to the others in doing a big thing that was just like blasphemous to the lore? Having Duncan loose his katana and use the dumb butterfly swords. The final battle was just not put together well, what they wanted to convey was poorly portrayed, that you /cant/ kill him... but useing magic sandstorm to bury him is not how you do that.
Edit: Also there are various small edited endings and lore conjectures to The Source - one was that if you killed the guardian, it would posses you like the dark quickining -and/or - you then become the guardian... so he had to stop the cycle (that apparently happened...once before? i.e the horsemen red scense flashbacks)
Okay, highlander rant over.
One thing about this: Dark Quickening and Richie's Death were two different events. The DQ happens late in season 4, Richie happens at the end of season 5. The apocalypse and evil power taking over the world stuff was supposed to be Season 6, but had nothing to do with the DQ that I know of.
It's possible Richie was intended to be killed during the DQ, and that the DQ was going to last longer, but they thought better of it (killing Richie was a pants-on-head retarded decision, BTW).
The creators of Highlander really wanted the show to be a "cop show" and they also had designs on eventually making it post-apocalyptic. You can see elements of both in season 1 and season 6 respectively, with neither going anywhere. Adrian Paul nixed both ideas, AFAIK, because he knew the fans would shit all over it.
The Raven spinoff was where they finally got to fulfill all their cop show fantasies. That show was pretty bad. It got decent towards the very end (like the last five episodes) of the one season it got, but it had already been cancelled. I think an S2 might have been solid, given the trajectory it was on. Oh well.
Not sure about the whole apocalypse thing and Ahriman and all that crap, but the idea of all the immortals being corrupted and coming out to take over the world IS kind of interesting. Especially if it had led to Methos being the big final boss, playing off of how he used to be one of the Four Horsemen. They got to that in S5 and it was good, but imagine if it had been during a big DQ arc where Methos is essentially reverted to his vicious past-self? I always had a feeling he'd turn evil again by the end of the show, but he didn't (and I'm glad he didn't, and he should have been the one to get a spinoff).
Interesting idea you have here that The Source is basically just repurposed ideas from the original plan for Season 6 (and 7?) of the show. Adrian Paul put the kibosh on it in S6 and then left so there was no S7, but I'm pretty sure the whole plan was a post-apocalyptic S6 and S7 probably with Methos as the end bad guy.
Even if The Source does have some DNA from this scrapped storyline idea, that DNA is being fitted into what appears to be a rejected horror movie script. I can't really give that movie credit for anything.