Yeah, I think Mario RPGs are the more creative Mario games. They have better sotries than the platformers, and really get you hooked on the game, having to know what happens next. I also liked how in PM:TTYD you got to know more about your partners, not just "They join you, so there". bobbery, would be a great example. And yes, even though Bowser is the main villain in quite a few of the Mario games, he always has something new up his sleeve, and still gives you that "I just beat a Mario game w00t" feeling.
“A wagon full of pamcakes? In the Champeen ship?! I’d like to see ya try!†~ Homestar Runner
