Creative, fun, immersive, challenging, amazing story and lovely story. I could pick one of these topics to describe how great is the experience to play Paper Mario TTYD, and I still would have to find another compliment to write over here.
It's incredible how this game managed to merge Super Mario, rpg system and super fun mechanics. It's not hard, neither easy, on the contrary, it gives a lot of choices to players to decide how to play/beat/enjoy this.
It's sure a game everyone should play.