Feels like I'm talking to myself again, but...
Shake it! > 1 > 2 > 3
I have a massive feeling I'm going to enjoy '4' much more than 1.
16 bit, super bright and colorful graphics(When playing on the DS LIte that is), wonderful art direction, the bosses look enormous and cartoon-scary ect ect.
However, I'm going to lay low on WL for a little bit....Because as of now I'm a bit Wario'd out from playing WL2, then KI: 3D Classics in between and 'then' taking on WL3 right afterwords. It's always important to space franchises out considering when these titles were released they were years apart. 
With that said, I could easily live without owning my copy of Wario Land 3(Doesn't exactly generate good gaming memories.lol)....Maybe even 2 depending.
Anyways! Seems like Shake Dimension, 4 and 1 are the best of the franchise. 


. I'm still playing the foist one, so I'm in no hurry for the sequels, but I sure hope Wario Land 2's not far off from the EU Virtual Console, plus America should get Wario Land 1 soon too.
WL4 insantly blew me away with the vibrant detailed and ultra colorful graphics and fantastic environemnts. The character animations are superb(Just wait until you see the bosses) and it just flows so much better than it did before.