Is the GoW2 campaign shorter than the halo 3 campaign? how long does it usually take to beat either one?

I have both games and in my opinion their campaign is almost of the same length, although it is hard to tell. regarding the time it takes to beat any of them it pretty much depends on the difficulty you are playing on and your personal hability. if you are playing normal i would say 6-8h depending. you should take note that the most playtime of this games will be given by its online multiplayer not from the campaign so whichever style you like the most you should get.