Squirmer on Windows 3.X
When I could find the arcade machine:
Centipede:
Number Munchers, because gaming in school, bitches:
Keen 4, platforming + pogo stick + ray gun = a game that needs to be remade:
I've always been a PC gamer /eyeroll
By grade school I was playing a fuck ton of Sega Genesis:
Sonic 2 and Sonic & Knuckles:
And NBA Jam, the best basketball game ever made:
I love emulating games, but one thing you miss out with emulating games is cartridge features. Remember that when you purchased Sonic & Knuckles you could use the pimped out Sonic & Knuckles cartridge to play as Knuckles in the other Sonic games? The cartridge looked like this:
Fucking sweet, right?
After the dark days of 2D gaming I spent many summers playing the shit out of Twisted Metal. I was a Play Station kid. Twisted Metal, Twisted Metal 2, Rogue Trip: Vacation 2012, Tomb Raider, Abe's Odyssey, Doom.
And then in ~1999ish I got into real PC games like Quake, Half-Life, TFC, and my mind was blown. Oh and Roller Coaster Tycoon. Damn I love that game. And Starcraft. And GTA2! Damn that game was fun.
Do I really have to pick
ONE game that got me into gaming? I can't do it! Gaming is huge part of my life. It is tied to love, friends, family, nostalgia, and good times. For me, gaming is way more than a hobby. Or it was. I've definitely put some other life pursuits first. =/ But I'll always have the memories (until I get Alzheimer's or whatever

).
EDIT: Can't forget Oregon Trail! Thanks Typhoid. Also ironic username for that game.