Underrated: World of Final Fantasy. This game is tremendous. The battles are pretty simplistic and it is never particularly challenging, but I love the way it re-creates so many classic Final Fantasy locations with a diorama-esque look and dream-like aesthetic. The soundtrack is also suitably mystical. So many of SE's modern projects feel low-effort or botched, while WOFF feels like it has way more effort and care put into it than it actually called for. It was supposed to be a fun little tribute game and it ended up being one of my favorite games of the last five years.
Underrated: Terminator Salvation, the arcade game. While it doesn't get my motor running the same way T2 The Arcade Game did, this is still a pretty fantastic light-gun game. It's totally different from the console TS games and features some machines that didn't make it into the final cut of the movie, like the proto HK Tank. The only downside of it is that it's expensive, and you need like $30 in quarters to actually beat the game. Still a fun time, especially with a second player (which makes it much easier).