Super Paper Mario. I liked the lack of rpg fights and more of the rpg level ups. Sticker Star just didn't apeal to me. I didn't like the "use stickers to attack" thing.
Super Paper Mario was the first Paper Mario I played, and without ANY criticism from having played the previous ones, I loved SPM so much! Now that I have played the other Paper Mario games, I understand why people didn't enjoy SPM as much as I have. When it comes to overall, ignoring what the games should have been, I think Sticker Star was not up to par with Super Paper Mario. That's just my opinion.