Games that gave you the most bang for your buck

No Fallout love?

I'd say the entire Fallout franchise has had huge re-playability, especially with the modding community for the FPS ones. New Vegas was a different game with addons. It was like 2 for 1.

Also, every final fantasy up to FFX-2 was always big bang for my buck.

EQ
Eve
Civ 1/3/4 (FFH mod is really what made 4 have such a long shelf life - still play it)
Warlords
StarCraft
Diablo
WarCraft II

Any Madden game? Ridiculous amount of playtime with those.
I think I had over 300 days played on my BL in EQ. High school is still a blur.
Final Fantasy 9 - I must've beaten this game about 7 times, and each time is probably 40+ hours into it.
Zelda:OoT and ALttP - Beaten each of these at least 10 times, never gets old.
SC2 - Dumped a lot of hours into this shit.
WoW - Especially since I don't pay for my own sub (raid leader bought me a year, idk why).
LotR: Battle for Middle Earth - holy shit did I play this game endlessly. Terrible, terrible game, but fuck me Rohan was so OP.

For me:

WoW/EQ. It really is hard to beat MMO's when it comes to money spent per hour played.
CS (can't beat free for original CS)
Mass Effect series (I've played through 1 and 2 probably 5 or 6 times each, 50+ hrs each time)
Civ 4/5
StarCraft 2
Final Fantasy X. Not the best of the series but dear god I have spent a lot of time playing it. Think I maxed out the clock on two different save files at 99:59.

Mass Effect 3 multiplayer element only. Considering it was an afterthought to the SP game I'm still playing it over a year after it's release and see nothing changing that anytime soon. Prior to that it'd be Adventure on the Atari, Chucky Egg 2 on the ZX Spectrum, Turrican on the Amiga, Goldeneye on the N64, and FF7 on the PS.

If we're allowing MMOs into the equation then FF11 would be mine. While EQ holds a place in my heart the world of FF11 was so beautifully polished I lost years of my life in it.

Tribes 1 - Shifter Servers
Ultima Online - Free Shards

Both free to me with hundreds of hours of gameplay.

Starcraft: Broodwar
Diablo 2
League of Legends

How could I forget Rise of Nations. Probably played that for close to 2 years. Very under rated RTS imo

I call those my "best buys" of the year awards. It used to be just pc games, but now I've extended it to any form of entertainment or tools.

In my gaming category:
1) Neverwinter Nights (including the two main expansions.
2) Mount & Blade
3) EQ
4) Blood Bowl (all three)

Neverwinter Nights: I know I have over 500+ hours played. Between the main campaigns, private servers, RP servers, DM guided games, my own modding work (converting it into 40K). I got so many hours of fun out of this game, I eventually got the platinum edition just to stay up to date. So far no game has dethroned NWN. NWN2 was a flop, I pirated the expansions in protest. Right now I'm entertaining the idea of updated the graphics so that I can use it to run our rpg games with it.

Mount & Blade: 500+ hours, way too many to even know. I know I played this game for years back when it was still alpha and all the new factions didn't exist. I played this game back when you couldn't join swadians or vaegirans, they were just some random armies wandering the map. I still remember the Black riders that would invade every once in a while. Aside from that I spent many months doing artwork for the 1866 mod.

EQ: nuff said.

Blood Bowl: My baby. I know I have as many hours played as some of the games above; steam says 275, but that's just Chaos edition. I had Legendary and Dark Elf edition prior from Direct2Drive.

Ultima Online would be up there as well as The Sims (original), but when I honestly look back I think the games above easily beat those in terms of how much use and entertainment I got out of how much I invested. Although some of those games on there would easily be dethroned by the mini's games I play.

List with rpgs and miniature wargames included:

1) Battlefleet Gothic (32,000 points worth of Imperial Guard alone, throughout the years gave away several fleets of different races).
2) Dungeons & Dragons 3.0 and 3.5
3) Neverwinter Nights
4) Blood Bowl tabletop

Aside from the obvious MMO stuff.

Gran Turismo 2: I played this game so fucking much. I learned to tweak gear ratios and camber and shit to eke out 1/10th of a second a lap on courses. And to get my Pikes Peak Escudo to 250+mph

Monster Hunter/Monster Hunter Tri: Especially MH1 on the PS2 though. Got the intranat shit just for that. Had almost the best weapons and armors for each type. Blah blah blah. I played the fuck out of Tri as well on the Wii, just not quite as much.

Dungeon Defenders: Initially played through and got pretty damn buff on Xbox, then got it through Steam where it was actually supported and ran through everything there. Over and over and over. They just absolutely nailed the formula of Tower Defense + 3rd person action + Upgrades/Looting. Wish they hadn't nickle and dimed so hard and constantly unbalanced the game to justify the new shit being worth paying for. Still, this game was the shit.

Diablo 2: Duh

Oh yeah and Super Mario Kart, didn't play as obsessively as GT2 but I did have to play non-stop long enough to always beat my brothers' times on every track. It was a LOT of play time...

Xenogears is not only the best game of all time it's also the game I've put more hours into than anything else and one of the few things I have ever replayed (normally I play through a game once and that's it).

Heroes of Might and Magic 3 : still playing 2-3 times a month
BloodBowl

Everquest
Early Command and Conquers
Minecraft : /
Mortal Kombat 9 (PS3)
mario party 3 (N64)
Warioland (gameboy)

Maybe I'll think of some later on

Dragons dogma, I never get tired of throwing my pawns or strangers off ledges and mountains.

GoldenEye
EQ
Culdcept
Dota 2

No particular order:

Sins of a Solar Empire
TF/TFC/TF2
HOMM series
Disciples 2 + expansions
Dungeon Siege 1 & 2
Total Annihilation/Supreme Commander

Path of the exile

Mass effect
Fall Out
Elder scrolls
WoW
EQ
Diablo 1 and 2
Never Winter