I am definitely most excited for Halo 2 and 3 (if they come out this year). Just the nostalgia of it all and being able to play them on mouse and keyboard :D. After that I'm really hoping Nioh 2 comes to PC this year as well.
Definitely would make playing Halo Reach look that much better! Crazy, playing Reach at 30fps 10 years ago on the 360 vs playing it now at 200+fps and on the master platform!