I'm gonna have to say Halo. I have only played the first one but it's a great game. Gears has a lot of pointless gore and it's not really my style. Halo uses blood tasty and too add feeling. At least in what I've played of it. I haven't played much though.
*Gears of War .II Vs. Halo 1,2,3 or the whole enchilada Vs. the whole enchilada?* Gears of War, it's far better than any HALO game...except the first, the first HALO: Combat Evolved was the best game ever, although it was a drastically improved Marathon.
However I'm a hardcore fps person, I like lots of blood and stuff like that so you can't really count my vote since Halo is extremely dry for my taste XP
Halo is the worst game to ever exist, truly. Gears of war 1 > Halo series no argument there. It saddens me to say GoW2 = Halo 3. they are both fail. I acknowledge Halo 2 is a great game, but Halo 3 ruined the series. Halo Requires no skill whatsoever. and they just plain ruined GoW2. Gears of War 1 is the winner. In my opinion of course!