So many it'd be impossible for me to even give you a break down of the old school games I used to enjoy playing, but I'll give you a sampling
NES games (there's probably 50 I love, here's a few):
Super C
Tecmo Bowl
Rush'n Attack (aka Russian Attack!)
Jackal
Ikari Warriors
Gun Smoke
Mega Man 2
Sega: Jungle Strike
Madden 94
ToeJam & Earl
Skitchin
Pitfall: The Mayan Adventure
Sonic the Hedgehog 2
Golden Axe
Zombies Ate My Neighbors
NBA Jam
Super Street Fighter II Turbo
Streets of Rage
NHL 95
Playstation:Resident Evil
Clock Tower
Metal Gear Solid
Gran Turismo 2
Grand Theft Auto 2
Command & Conquer: Red Alert
Games like San Andreas for PS2 are still always going to be some of my favorites. I can honestly say that at the time of me playing any game that had been released up to any point when I'm playing a game, San Andreas was my favorite game ever. So many nostalgic things about the game, and time of my life. Put so much time into that game it's ridiculous. Even played the Cops n Robbers mod for SA on my computer years and years after playing the game on PS2.
Then there's games on my PC from the late 90s and early 2000s I love. Such as Ultima Online, the first Tom Clancy's Rainbow Six game (spending so much time prepping your team to go to check points and do certain things, only to have one get fucked and have to go back and modify it). By far the most enjoyment I got from a game was Half-Life and all the free mods that I got to play because of it, most notably team fortress classic being my first baby, and then Counter-Strike being my next (but also games like Firearms, FrontLine Force, Day of Defeat, Insurgency mod, Pirates Vikings and Knights, Opposing Force CTF, the list goes on and on).