Donkey Kong Country Tropical Freeze
I bought Donkey Kong Country Tropical Freeze for Wii U and it was probably my favorite game for the system. The levels are clutch and the devs did a great job creating fast-paced and smooth obstacle courses that are interesting to explore and compelling to run.
Revisiting the game in 2 players was a frustrating experience, though. We couldn't beat a simple boss and navigating platforms was a hassle. Then I sat back, watched my friend play and saw that, yeah, the game really works best as a solo experience. Stringing together jumps and rolls is great fun, and the levels are meant to played in a nice, continuous flow.
Good luck getting those shiny gold medals and all the puzzles pieces. There is a lot replay value thanks to all the extras and top tier level design. The music seems to sync with the pace of the characters' movement, or maybe it's just awesome. Confirmation required in the comments section.