Just looking at the 360 list points out why, as has been brought up before (and I agree), PC gamers really shouldn't bother getting a 360. 6 of those 10 games are available on PC, with little doubt that at some point Halo 3 and Mass Effect will come to PC too (given Microsoft's and Bioware's previous doings). Rockband and gh2 are available on other systems, so there is very little incentive to buy a 360.
I'll admit this is a shame, because there are a few titles on 360 I'd love to play, but I really can't justify the current prices for the handful of games that I'd be interested in.