I like Treasure games, but I agree with OptOut that they are overrated. To me they inhabit the same space as companies like Compile, TechnoSoft, Falcom and Quintet. They made fun games when they stuck to the types of games they were good at, but when they deviated from that, their games just came off as cumbersome and disjointed. I mostly blame Sega fans for the Treasure hype, and I think a lot of those games listed rode the coat tails of Gunstar Heroes and Radiant Silvergun. Remove those games and a couple more and you aren't left with much that's very interesting IMO.
Ironically, I really like Wario World.