The great thing about Mario's RPGs is that they are RPGS with GAMEPLAY. I don't consider 'select a command and wait 3 minutes for the animation' to be gameplay. RPGs are generally story-driven games, because if you took the story out and left in the 'select a command' "gameplay" the game wouldn't be enjoyable at all.
With the GBA/DS Mario RPGs, you could possibly go through the entire game without ever being hit, because the whole system is based on reactions and timed button presses. I can assume that the other Mario RPGs are similar, *and* they're funny. The stories may not be the deepest or most inspiring, but the humour and gameplay (in typical Nintendo fashion) more than make up for it.

Super Paper Mario is a spin-off of a spin-off merging with another spin-off. Everything is derivative