10) Fable II
9) Mario & Luigi: Superstar Saga
8) Freedom Force
6) Star Wars: Knights of the Old Republic
5) Disgaea DS
4) Paper Mario: The Thousand Year Door
3) Kingdom Hearts
2) Fallout 3
1) Diablo II
The top game on my list was never in doubt. I played Diablo II (including the Lord of Destruction expansion pack) for at least five years, and I still carry it around on a USB drive, ready to go at a moment's notice (the last patch means I don't need the CDs). In fact, I'm sure that few, if any, of my choices will be shocking. Fallout 3, Kingdom Hearts, KotOR, and the Mario games I've chosen are loved by many, and although you hear complaints about Fable II, it's still a great, fun game.
On the other hand, some of my favorites aren't as widely played, and I think they should be. Torchlight is a recent game, and while it doesn't do a lot of unique things, it does just about everything right. Disgaea DS may be a remake, but it's one of the few DS games I've played that makes really good use of both screens, and a great game to boot.
And Freedom Force. To this day, it's the RPG that has made me feel the most like I was leading a super-powered team. It's not flawless, but it's definitely worthy of a spot on my list. Its character creation system in particular holds a special place in my heart. You have complete freedom, but the stronger the character you create, the more prestigious your team needs to be in order to "recruit" him/her. I love that balance.