Wario Land: Shake It is definitely a good platformer that does not happen to be very innovative though
1) Pure 2D fun. This is a classic platformer and it's really great that Nintendo decided to go for the 2D instead of the non-satisfying 3D stuff.
2) Nice stages
3) Great controls
4) Absence of lives whatsoever. This is not to become a constant pattern of platformers, but it's rare to ifnd.
5) Challenging final boss
6) Great replay value for those who want to beat this game 100%
Disadvantages:
1) Not very impressive graphics
2) Too short (only 5 world and the boss, are you kidding me?)
3) While finding the three treasure chests is alright, some of the challenges are kind of repetitive and blunt.
4) Lack of Waluigi. It's about time Waluigi accompanies Wario in a platformer.
Overall and despite the good controls the game is not very innovative. It is a must have for those that love the old style platformers, but don't expect to see something you haven't encountered in previous games.
A great idea for a sequel to Wario Land: Shake It would be the use of Waluigi and the old favorite Wario Bike in stages where you can ride it in an urban environment stuff.