Gears of War is, by far, my favorite X360 exclusive of all time, and is one of the best games from last decade.
PROS: Epic Campaign. Fantastic Gameplay. Lovely Graphics. Multiplayer is a lot of fun. Soundtrack is amazing. Great use of a chainsaw. Bad-Ass Characters.
CONS: Can be difficult at times.
For 2006, the graphics were AMAZING! But even todays standards, it still really holds up really well. It even sounds great too, thanks to the awesome soundtrack, it can be gritty sometimes, but it also keeps you moving, and is just awesome to listen to.
The campaign is still alot of fun to play thru, especially with a friend. 2 Player Campaign is alot fun. And how they did it to make it fell not-so in Single-Player is well done. Now the gameplay is over the shoulder, take cover shooting. Basic stuff today, but back in 2006, almost no-one did this. Theres also driving stage, and some awesome boss battles. And the character themselves are just bad-ass, like Bad-@$$!
And need i mention the greatest use of a chainsaw ever? You press the B button near an enemy, and behold...Epic-Massacre!
The online multiplayer, back then was fun. But now, a match will be over before you'll know it because people are so good at the game, that they can finish an online match in like 30 seconds.
The only downside is that, it can be rather difficult at times. Like....really. Especially later on in the game, and the later boss-battles. But thats just a small negative.
Gears of War is my personal favorite exclusive for the X360. The sequel was great. I have yet to play #3. But i will soon. Gears of War is one of the best games from last decade. And if you haven't played it yet. DO SO! Buy it! And have fun.