ok so can halo 3 accounts get banned from a large number of betrayels.

yo my gamerscore is justin 351 and it seems that every time i win, my skill goes down and when i loose it goes way up. for example: my skill went from 19 to 18 and the next game at high ground i got 22 kills and led the team. guess what, it didn't go up. however, when i got way more deaths than kills in one game it went to 19. wtf

im thinking of getting gow2 and cod5,whats a couple other good games i shoudl get