You forgot about Battlerock Galaxy as well.
Funny thing is, that's the one I linked to first, but then I remembered this harder (for me) level which auto scrolls and uses the same theme. But either way yeah, the purple coin level are annoying. The ones that require 100 -exactly- in particular. At least none of them really take a terribly long time to redo, but still.
As far as the Mario & Luigi games go, I started playing Paper Jam a few months ago at some point. I always liked the combat system in these games, but never got around to beating this one for one reason or another. It did remind me a lot of Paper Mario for obvious reasons but I got a lot of "been here done that" feelings from it. I also had the first M&L game for GBA when it came out, but I did not really like turn based RPGs at that time, besides Pokemon, and Paper Mario, that is. Plus I remember being just generally bad at the timing/ reaction based combat system then, but now, I really appreciate it. I think why I liked Paper Mario more besides, you know, being on a TV was that it wasn't as integral to have good timing in battles, especially defensively. Sure it helped, but it was never completely required save for a very select handful of spots (Flower Fields boss, final boss, and the optional dojo guy, or any optional boss for that matter).
Honestly, the only Mario RPG of any sub-series I've ever finished was Paper Mario which I play through every year or three. 
EDIT: I went back and started playing Paper Jam again, and I remember exactly why I stopped. Two words. Paper. Toads. Who thought that searching for stuff was fun? Who enjoys pixel hunting, that is mandatory to advance? I hated this, and do not like games that do this. This extends to the drops of light in TP, and really, any level where you are required to hunt stuff down for no reason (Knuckles' and Rouge stages, 8-red-coin stars, etc). It's not fun, and is a waste of time. It feels like padding. Oh, instead of a new area to explore, nope, you just have to go into this area and find stuff, yay. Can't find them all, and want to leave? Cool, you get to start over. I am willing to beat this game by using a guide on these parts, cause everything else is really nice.