I give my opinion based on a few factors, bearing in mind that:
a) I haven't had the opportunity to play that many games this generation.
b) My choice probably isn't the best-made game I played this generation, but one that I was compelled to continue playing to completion.
c) There are just too many games released in a generation to make a decisive choice on this topic.
Kirby's Epic Yarn doesn't tell an intricate story, have a complex or revolutionary gameplay system, or even provide anything new to its genre. What Kirby's Epic Yarn does is provides a technically sound platformer that encourages you to explore the levels, all in an art style that is unlike anything I've seen in a video game, and that looks better than a lot of the games on the HD systems because of it. Additionally, the soundtrack (mostly in piano) provides an extra layer of character & personalty to a game that's already brimming with charm. On top of this, the gameplay is strung-along by a storybook sequence of cutscenes spoken by a narrator that adds the finishing touch to a game that compelled me to play continually with my wife with a childlike excitement to see what's next, which is something I rarely experience playing games anymore.
A game doesn't have to be a revolutionary shift in gameplay design to be considered top tier, sometimes it just has to refine a tried & true formula to its core and deliver it in the best package possible to leave a mark.