C64:Beating Ghost n Goblins one day on Commodore 64 when I was 9 or 10. Dad came home and didn't believe me and I was able to do it again on first play try. First time I ever remember my dad being blown away by something I had done. Knowing now hard hard that game is, I'm kind of impressed by it too. Lots of C64 memories with dad. Temple of Asphai, Pool of Radiance, Archon, Pole Position, Beachhead...good times.
NES:Playing Dragon Warrior for months on end. Saving up money for a couple months to by Final Fantasy on NES for $42. Beating Battletoads. All nighters with cousins, drinking Jolt Cola all night playing Ice Hockey, Punch Out, Adventure Island, Mario 2 and so many more.
SNES:Being blown away by the graphics at the time. Hours upon hours with Secret of Mana, Final Fantasy's, Chrono Trigger...so many good RPGs with my buddy Tuyen. Still friends with him, still talk about our gaming days back then...great nostalgia.
Playstation:Teenaged drug and alcohol fused all-nighters. Vigilante 8, Jet Moto 2, Tony Hawk Pro skater. Many good RPGs...Final Fantasy Tactics.
Playstation 2 / XBOX:So many games! Modded xbox MAME parties were a blast.
Xbox 360/PS3:Online Halo all-nighters. Massive game variety. Culdcept Saga binges. Disgaea fun. Gears of War campaign duo's with good friends.
PC:Has been there since the c64, 386 days. Too many memories to even count...single player, LAN, taking turns with dad/friends, MMO's. Main form of gaming nowadays.