My favorite game of generation (and all time and decade) is Bioshock Infinite. The ending is probably one of my favorites of all time and Troy Baker plus voice of Elizabeth just - it was too incredibly good. Makes me wonder what 2K has planned for 4. I'd love for them to go off the rails, but I'll bet they use an obvious framework so they can continue to monetize the IP.
Bestgame of decade objectively (tech, visuals, narrative, story, varied gameplay, music, level design, atmosphere, characters, world building) is Witcher 3. Absolutely ruined other RPGs for me. Nothing out there is like it. Makes me so incredibly excited for Cyberpunk, which I know will be delayed.