It's a bit too early for me to say yet, seeing how Sticker Star has just recently came out compared to Partners in Time. Over the years, I've found Partners in Time more fun to play again with each passing year (or two). I personally find it to have aged pretty well.
PiT. It definitely has it's fair share of flaws, but it's still a solid game regardless. It has creative bosses and enemies, an original story by Mario standards, decent humor, and I just find the game all around fun.
Quote and Curly Brace for Super Smash Bros 4! Appeasing an unlimited amount of chocolate . . .