How anyone liked anything in Super Paper Mario outside of the story is beyond me.
That's just it; the story and characters in SPM were enjoyable enough to let the gameplay get a pass. There was actually a reason to keep playing; enjoying the story. Even so, the gameplay is nowhere near as bad as SS's. It wasn't a redundant cycle of battle to get coins, use coins on stickers, use stickers in battle, get coins, etc.; there was an experience system and the characters actually got stronger from earning enough points. Sticker Star just slapped some stripped down turn based system in the game that offers no incentive to participate in, threw in bosses that were actually cryptic puzzles in disguise, made things their only weakness, made cryptic overworld puzzles that are solved with things; but only the correct ones, incorrect ones get wasted instead of returned to your album AND threw out the focus on story and characters.
However, since some people are getting anal about people disliking the game and calling them trolls and haters who blindly dislike the game before telling them to suck it up and quit whining and seem incapable of actually reading the parts where legitimate reasons for hating the game(see: above) are given; I'll list what I think is decent:
The music is okay. It's not the best, but it doesn't suck, either.
The graphics are pretty good. I like the heavier emphasis on paper with cardboard structures and such.
There is a bit of humor in the weak dialogue; Snifit or Whiffit was great, but is buried in the pile of mediocrity that the rest of the game is.
That's pretty much it. There is not enough to justify this game being shoved into the Paper Mario series, nor is there enough to justify a forty dollar price tag.