A Link to the Snitch said:Wario Land II.
Wario Land 2 would be better than Wario Land, because it fully establishes the Wario franchise as one that is separate from Mario, and not just because it's the sequel to the first Wario Land -- it's the first Wario game in which he really becomes the outrageous character that we know today, as well as tearing away from the traditional Mario-esque gameplay that was in SML3.
WarioWare would obviously be the other choice, if it was allowed.