mmm I'll give this a shot. Maybe not 10, but here's some good ones.
Golden Sun
It's been mentioned here already, I'm happy so see =D. Golden Sun is probably a top contendor for RPGs with Final Fantasy. The story is epic, the battle system is fun, the Djinni system is different then mosts, and the puzzles can be rather challenging. Shame it hasn't gotten a 3rd one yet. Final Fantasy is great too, but everyone else said that, soooo...
Legend of Zelda: Ocarina of Time, Super Mario 64
Probably the best adventure games out there in addition to what everyone else is saying.
World of Warcraft
I'm a borderline addict

. But this game is such a great MMO. 80 levels of amazing zones and leveling system so far, and then raid and PvP content that could keep you playing for a very long time. 11 million players to back this up, too.
Paper Mario
Humurous dialogue, EXCELLENT fight system (action commands make this game so cool), and just over fun RPG here. How cool is it to be a paper man beating up some giant dragon, ya?
Super Smash Bros. Melee
If this had Wifi I'd be much more inclined to bust it out than playing Brawl. SSBM had a much smoother, faster, crisper fighting style that it's prerequisite and sequel. This is the best fighter out there IMO, though Brawl is nice for it's minigames, more characters and online play.
Spore
I could spend days on the creator screens alone; there's so much imagination to be spent in this game. That alone is probably what makes Spore so cool, though the progression seems rather repetitive, even with your own, different monsters as a player or NPC enemy.
Tetris
Same as what OP said.
PS I finally learned how to play the tetris music on marimba and euphonium lol
Fire Emblem
10 games of this out there should say enough. The story is great, the gameplay is fun, and there's so many ways to make this game different each play through.