Accidentally deleted my post... will try and recreate...
Heroes of Might and Magic 3: Still play today
WarCraft 2: I actually purchased Kali, which was a service to enable multiplayer on games that only had IPX/LAN multiplayer modes - Duke Nukem and WarCraft 2 being the most popular. Long before Battlenet...
Civilization 1-5 (6 sucks): I still play 5 a lot... 4 might be the best of the series though...
Wing Commander: Recently downloaded from GOG - still a ton of fun to play
Monday Night Football: Years ahead of its time, I still hum the old themesong when I'm watching football on TV
My defensive line was awe-inspiring (simply moving your lineman a step to the right or left before the snap virtually assured you of a sack!).
Faceoff: Best PC hockey game ever, also years ahead of its time - and I still have the themesong in my head to this day!
Hardball 2: Accolade made the best games, including this one, the best baseball series ever made for the PC - 2 was heavily focused on stats (which made it my favourite), whereas 3-6 focused on graphics...
Lakers vs. Celtics: Made when PCs didn't have the processing power to have 10 moving players at once (players basically just stood still if they didn't have the ball - or ran to predetermined locations), this was the best basketball game - long before NBA Jam!
Fifa '96: This game actually made me build my first dedicated gaming PC - Pentium 166 with 16MB of RAM!!! 16MB!!! That was INSANE!!!
StarControl: Apparently they are making #4 - I'll be watching!
Elder Scrolls 4: I prefer it to Skyrim, and am still playing it
NES/Gameboy/N64: Super Mario Bros, Duck Hunt, Mike Tyson's Punchout, Tetris, Mario Tennis - I still remember playing Gameboy Tetris against a buddy who refused to stop playing until he won a match (they were best 4/7)... ended up playing until past 2am....
Special Mention to the Freeware game "Pong Kombat", which was simply Pong but with the ability to fire missile weapons (and do fatalities after the match). Your paddle would match the colour of a Mortal Kombat character, and the cheezy voiceovers were classic.