10. Master of Orion II * Microprose (PC)
GalCiv2 will probably pass this once I get the new econ down and parameters figured out. Until then, it'll hafta sit at #11 behind a PC game I've been playing for over a decade. The biggest complaint I had about GC2 was that the races didn't seem different enough. In MOO2, you felt the difference between about half a dozen of them.
9. Street Fighter II [series] * Capcom (Arcade)
8. We

Katamari * Namco (PS2)
Simple yet addictive...and you always think you can do a smidge better. The same thing that made Tetris so great, but with wacky Japanese humor. More stuff to do than in the original, which is why the sequel gets the nod.
7. Combat * Atari (2600)
The purest, and thus most fun, multiplayer game. Tanks, bi-planes, jet-planes, choppers, bouncing ammo, invisible ammo, invisible walls, invisible planes...with that much variety, I don't see how I coulda ever got bored.
6. Super Mario Bros. * Nintendo (NES)
5. Samurai Shodown II * NeoGeo (Arcade)
I always liked it better than Street Fighter II. I think it was either the anime-ness or the swords...or maybe because the arcade near me at the time had it and not SF2.
4. Final Fantasy Tactics * Square (PSX)
Still the best, most fun, RPG I've ever played. Every time I pick up an RPG, I like the parts that remind me of this game, and every RPG I find wanting in comparison to it.
3. Harvest Moon: Back to Nature * Natsume (PSX)
It is far and away the most educational game I ever played. Got me eating vegetables, cooking for myself, and drinking green tea. Story and gameplay that suck you in and full of characters I found myself being very attached to. Still playing the new HM games, but none have captured my heart like this one.
2. Super Dodge Ball * Super Techno Arts (NES)
Still the greatest arcade style sports game ever made. I remember playing this all day for weeks in three different summers when I was a kid. First video game I really geeked out on.
1. Galaga * Namco (Arcade)
Possibly the ultimate arcade game. Perfect speed. Perfect enemies. Perfect controls. Perfect sound. I just wish I were good at it.