I can definitely second Trackmania, Jedi Academy (though Outcast as well) and AOE II... and of course FL. These are games I can always return to with a smile on my face.
Discounting FL Disco, here they are - bear in mind that I'm old as dirt...
Computer games: MultiPlayerBattleTech(all versions) - Best damn mix of RolePlay and tactics I've ever seen. Ever. Everquest(not EQ2!) - I played the shiznit outta that one. Cost me a couple jobs and a fiance too! [color=#FFCC66]Tie Fighter(or Xwing vs. tie Fighter) - Wish I could find a version that works on today's systems! [color=#FFCC66]Crimson Skies(PC only - the console versions sucked arse) - Way too cool for words. [color=#FFCC66]Mechwarrior 2 - I can still hear the voice "Overheated, shutting down..." oh, god, no..... [color=#FFCC66]Ultima 1 & 2(on the Apple 2+) - Damn your eyes Lord British! I should have been studying my college exams!
[color=#FFFFFF]Tabletop Games: The Awful Green Things From Outer Space - Just good fun! [color=#FFCC66]Car Wars - I still remember a motorcycle gang assault on a tanker group that lasted 12 hours [color=#FFCC66]Dungeons & Dragons(of course) - Days, weeks, months... ...just gone forever
[color=#FFCC66][color=#FFCC66]Magic: the Gathering - I still have a deck of cards 11 inches tall, somewhere...
There's more in there that I've forgotten, but those are the ones I have vivid memories of playing, so I guess that makes them my favs.
1. Mass Effect series
2. Far Cry 1
3. Codename: Panzers Phase 1&2
4. Rome: Total War
5. Medieval 2: Total War
6. Empires: Total War
7. Unreal Tournament 2004
8. Freelancer
9. World of Tanks
10. Need For Speed Most Wanted
11. Need For Speed Underground 2
12. Blood Rayne 1&2
13. Battlefield 2
14. Guild Wars
15. Silent Hunter 3
16. Hitman series
17. Homeworld
18. Sins of a Solar Empire
19. Star Wars: Jedi Academy
20. Battlefront II