Be honest!
What games that come out with yearly iterations do you buy? As for me, I continually get sucked in to playing the new Assassins Creed every year. But I've slowly realized that they've continually gotten lazier and lazier and the series has lacked innovation. Therefore I will no longer buy it until it does something truly groundbreaking.
Besides that, the only other one I get every year is the NBA 2k games. I love basketball and I think that 2k Sports does an admirable job of recreating the ins and outs of the game of basketball in videogame form. Fantastic presentation as well. I always look forward to NBA 2k and buy it at launch every year.