Gore is good.
Gears of War is a grand triumph of video games and the action genre. Its gameplay is truly close to perfect, only some minor (but annoying) glitches ruin its 10. In addition to being just plain fun to play Gears of War has beautiful and bloody (mostly bloody) graphics and a good soundtrack. Music is not comparable to Halo's but few things are. The game is hard but not far beyond the reach of the non-hardcore. Cover tactics actually ruin higher difficulties, taking away campaign's challenge to any reasonably experienced player. There's not much of a story but the seemingly one-dimensional characters are actually quite believable and, in many cases, make the game all the more worth playing. However, Gears of War suffers the plague of the action genre (books, movies, and games), it doesn't take very long. Certainly it's not probable to beat the campaign in one sitting but maybe one day.
But beyond the campaign is the addictive multiplayer. Again, in this category, Gears of War falls short of the Halo series but there's most certainly a reason Gears of War is number one on Xbox Live (and it's not because of the chainsaw).
Let me make one thing very clear: Gears of War is not a copy of Halo, not even a medium sized amount (maybe a small amount, they're both Sci-Fi Shooters). Gears of War is all about the cover and keeping distance. Halo is about wading straight in to the fray and creating a pile of dead. The reason I make references to Halo is because both Gears of War and Halo are similarily amazing games.
Gears of War has my highest recommendation to any action fan. Kick some ass, and leave trail of bloody bits and thermo-round ridden corpses in your wake.