I like that Schafer posted a picture of fallout 2 twice, it scores twenty out of ten
I'm going to try and list some games that haven't been mentioned or haven't been mentioned frequently.
Quake 2 - great online at the time and great mods like rocket arena and action quake 2. This is the game that united my gaming friends the most. Today i don't think it holds up as well, quake 3 just has a better engine feature wise(brighter, forcemodel options, it gets in the way of desired gamplay less) and I think aim feels better. The maps also feel too big for one on one.
Quake 3 CPMA mod - i'm not good at it but think it is probably as good as a competitive FPS of that style can get.
Honorable mention to Warsow because it's very similar to CMPA and has great unique features. If it ever gets a release with a large map set it'll be a 10.
-dash, walljump, dodge button adding more tricks onto maps and even more movement options
-ammo packs ammo does more damage than weapon pickup ammo leading to more map usage.
-Capture the flag with 8 second flag return rule unless a team mate is in the enemy base holding the counter. Flag runners either need to be able to move at the fastest possible speeds or have help.
All the Lucas Arts adventure games i've played while they were new - sam and max, day of the tentacle, indiana jones and the fate of atlantis, and full throttle. Great stories, fun puzzles.
Firepro Wrestling 2 (GBA) - one of the two english releases of this great game. Great edit mode, such high detail. The AI you can put into a wrestler is amazing. The perfect mix of a simulation and a for fun game. Audiance rank mode let you pick a style of fans and try pull off the perfect match for them, no squashes unless they were MMA fans. This is one of the few single player games i've played where
working the match(or whatever the game has) is not only possible but more fun than trying to win. Even in concept the only way to make a better game would be if a 3d KOC style system with multiple grapples was as fluid and dynamic as real life.
Maybe I will come back with a few more tomorrow