New Super Mario Bros. 2

[Gors]

Honestly, I think that the jump from SMB to 2, 3 and World, in terms of gameplay, increased in a similar size to the New Super Mario Bros series. Of course, a difference in visuals would be always a plus and doing away with some of the conventions, such as stomping the boss 3 times to kill it, or some of the visual styles would prove to be interesting.