Best Xbox Live multiplayer

this is a tough question for some people, but i just wanted to see everybody's opinions.

since gears of war and UT2004 have been a complete success, epic has finally unveiled their masterpiece Unreal Tournament 3. this game has a chance of tieing or topping halo 3 on xbox live

now since halo 1 and 2 have been a success both single player and multiplayer, multiplayer in halo has changed console gaming for a long time and alot of people still play it.

but which game would you think would be best on live, think bout it:D