what game makes the xbox360 worth getting

my friend is thinking about getting a 360 but not sure for what reason so can you help me out and list down the games that make the 360 worth getting.

The online play is what seperates the 360's superiority to the PS3. Thats why I think its worth getting. The online play is just faster, funner, more organized and has more options. Some games that would be worth getting Gears of War, Rainbow Six, Call of Duty 3, Forza Motorsports 2, Halo 2 (Xbox Original game) and theres some others ones out there I just can't think of right now. Then theres a lot of great games or "supposedly" great games coming out this year such as Halo 3, GTA IV the Madden and NCAA football games to name a few