Gears of War for the Xbox 360 is a great action/shooting game for a variety of reasons. The campaign story mode is pretty fun although the story is a bit generic at times. The game really shines when played with other people; my roommate and I had hours and hours of fun playing through the game on the multiple difficulties.
The online team-based mode is also really fun although with the recent release of Halo 3 there are not as many people playing Gears of War online. The game still has a loyal following though and it can be a lot of fun to jump online and chainsaw enemies.
Gears of War is incredibly violent, which is one of the major appeals to some gamers, and the weapon variety is nice and fairly unique. The graphics and audio effects are still amazing and very few games come close. This is definitely a game that every 360 owner needs to try at least once.