HALO 3 is definetly a system seller. Gears of War was great but HALO 3 makes you enter the world as Master Chief =)

User Rating: 9.5 | Halo 3 X360
When I played the first two levels of HALO 3 I was not so much impressed. Not saying that the graphics would be bad, but somehow it did not give me the WOW unlike Gears of War did back then. But the more you advance you can clearly feel the increase of atmosphere and graphic overkill. The Sound is also very nice and you will grow on Master Chief if you haven't played HALO 1&2 before. The vehicles are great especially the Scorpion Tanks of the Marines are much fun to drive and to shoot. Also carrying the heavy mounted guns where you play in 3rd person is also fun.
When you have finished the campaign at several difficulties, you still have lots of fun playing it online in various modes. You can even customize the online maps!
If you are not a first person-shooter hater and love the look of the Marines from the movie ALIENS, this is definetly a must have!