Since I've got nothing to do, I'll give a reason why each one is on my list
1. Final Fantasy VII - Not to this day have I felt so involved with a games story line and characters
2. Ocarina of Time - A cliched but well well presented story with great puzzle and combat based gameplay
3. Ninja Gaiden - The fastest and deepest combat in any game I've played
4. God of War - An epic and beautifully told story with incredibly fun and varied gameplay
5. Halo - A near perfect blend of tactics and action along with many minor details make this one of my favourite fps games
6. Freedom Fighters - A great shooter that seems somewhat under rated. Fantastic squad based gameplay, a unique story line and large scale levels make it a great experience.
7. Half Life 2 - One of the few games that's absoloutely fun from beggining to end. The variety in the gameplay is something that no game has managed to achieve to this day.
8. Powerstone - Why the hell haven't more developers created beat em ups like this? Probably the most original fighting game I've played, fantastic in multiplayer.
9. Shenmue series - Very original, and despite the fact that on paper, the games sound very dull, the way it's put together makes for a very addictive and interesting game.
10. Jade Empire - Amazing story, interesting and well voiced characters and a beautiful setting make this one of my favourite RPG's.