I 100%'d Wario Land 3 and that was one of the most satisfying experiences of my gaming life. That entire game was quality. Probably in my top 3 Gameboy games of all time, and that's saying something.
Since then, I always wanted to play the other Wario Land games, but was never able to find them in stores. Thank God for the Virtual Console. I played and finished Mario Land for the first time last year, and am making my way through the fantastic Land 2 right now. Wario Land and Wario Land 2 (which should be out in North America soon?) are next, and my expectations are pretty high :D