Mine would've been either 1001 Spikes, Isaac Rebirth or Shovel Knight. But since the first 2 are remakes mine GOTY is Shovel Knight too. Second is Rebirth and last is 1001 (Nicalis had kinda big year.)
Best game that came out this year, or best game I played this year? Best game that came out this year would be 1001 spikes. I unfortunately haven't beaten 4-4, 5-4, or 10-4(and the levels that follow), so I still haven't unlocked Curly or Jim. Best game I played this year would be the same as every year: Cave Story (who's 10th anniversary is tomorrow).
Best game I played this year was Monaco: What's Yours is Mine (but that released last year, so by most standards it doesn't count).
I pretty much only played two games released this year that were memorable, and that would be Kero Blaster and Luftrausers. So I guess that's my tie-pick for GOTY.
Might be a bit of a stretch, but for me it would be The Sun and Moon. After winning Ludum Dare 29, the developer went on to expand it into a full length Steam game. The gameplay is quite ingenious and the expansive map unlocks multiple levels when you beat one, which is good for a difficult game. It manages to change its aesthetics without being too distracting, at least as far as I know from playing it. Definitely worth checking out if you enjoy these sorts of platforming challenges.