Tough call and yet I've not played all the games I wanted to play. So far, I have FE Awakening, Sm4sh, Splatoon, and Xenovlade Chronicles X so far up there in my best of generation games. It's hard to choose. You got one that really got me hooked into the franchise, one that was able to balance competitive with casual and create possibly the greatest crossover roster ever assembled, an addicting and competitive online multiplayer game with a solid single player campaign, and the biggest game I've ever played yet. And i haven't gotten to play Witcher 3, Bayo 2, ALBW, BotW, Bloodborne, Sun and Moon, etc.
Pokemon Y, Mario Kart 8, and Mario Maker are honorable mentions.