Wow so many to choose from.
Arcade: Gauntlet, Punchout & NBA Jams
Atari: Donkey Kong and Pitfall
Nintendo: Legend of Zelda, Mike Tyson's Punchout & Tecmo Bowl
N64: Super Mario Bros. 3, Ninja Gaiden & TMNT
PS1: Resident Evil & Madden Football
PS2: Navy Seals, Syphon Filter, Red Dead Revolver, MVP Baseball, NCAA and Madden Football, Hot Shots Golf & Dynasty Warriors.
PS3: Elder Scrolls 4 Oblivion and MLB 2K7
Oblivion is now my favorite game ever and the one that currently has me acting like a Skooma (Game reference) Addict. I have been playing it about a month and a half or so now and I am hooked so bad that I haven't even been paying much attention to S/T. I know it's a big sin but this game is phenomenal. Makes me wished I had played it earlier on the PS2.