For my money, Ori and the Blind Forest is still the best game this year. There is a lot of stiff competition for it to stay top of my through list this coming fall, but right now, I just haven't enjoyed my experience with any other game quite as much in 2015.
If you haven't gotten around to the game yet, you might want to hold off just a little bit though. During GamesCom, Moons Studios' Thomas Mahler, revealed to Major Nelson that a new expansion is coming to the game with all new content later this year. On top of that, a definitive edition will be coming to Xbox One and Windows 10.
Not much more was said than that, but this seems the way to experience this game.
I can't recommend this title enough. It is charming in its level design and it's absolutely stunning. If you have the platforms for it, you owe it to yourself to give it a go.