One of these screenshots is from New Super Mario Bros. U. The other is for New Super Mario Bros. Wii. Can you tell which is which?
Click to enlarge.
Try these too:
How about these?
The Wii U image is the first shot in all the comparisons. What you can't appreciate at this size and resolution is that the Wii U images are made to appear in high definition; the Wii images don't. And the games are different in other ways. The Wii U game has special score-attack modes and lots of special Yoshis. It also has an elaborate overworld map reminiscent of Super Mario World.
Shall we compare them in action?