1. PS1. I spent many an hour getting my arse kicked playing Tekken 3. Also Allundra, FF7, Castlevania: SOTN and many others.
2. Dreamcast. Though I no longer have my original DC I have one I picked up at a thrift shop for $7 i still fire it up to play MvsC 2, Worms, Ready2Rumble, Tony Hawk 2 and a few other games. When I first played it I thought to myself "Now THIS is next generation right here!".
3.NES. I was the happiest kid in the world when my father got me Super Mario Bros 3 for my 11th birthday. That and playing Bad Dudes and Super Dodgeball with my brother. "I'm BAD!"
4. Atari 7800. I bought a 7800 new with money I had saved up doing odd jobs for my parents. After hooking it up I spent many hours playing Pole Position II, Galaga, Ms. Pac-Man, Asteroids and MAD/Atlantis/Missle Command.
5. Game Boy. The original green/yellow screen ones. Long bus trips and waiting for my parents to pick me up after school in highschool were alleviated by spending some time in Jurassic Park or playing Tetris or Legend of Zelda.