New Super Mario Bros. U Deluxe
This is a re-release of the Wii U Mario game. We played this game co-op from start to finish, which usually ends up with one of us accusing the other of deliberately causing their death in a myriad of scenarios. You jumped on my head, you pushed me into that goomba, you made me slip off this ledge, you took my mushroom... but when you're not fucking killing each other it's pure 2D Mario and the level design here is really really good.
Say what you will about the cornball art style of these modern Mario games, they still know how to make it fun. The fact that you can run this one with up to 4 players is kinda nuts. Worth playing solo, although I will say after completing it co-op I dropped my solo quest because nothing really changes. This comes with another game as well, which is Super Luigi and it's basically the same game with remixed, more challenging levels. All around a good game.