You know, for a lot of the "can it top Galaxy (2)" posts, I always wonder if in general the gaming public can ever be happy with a game that's has it's own indivudual strengths. Not just this game, but other games in long running series as well. I'm no different, but sometimes I take a step back and ask myself why I just did that and don't appreciate titles on their own qualities.
That's the best way to think about things, I feel. Things is, this game has already topped Galaxy in its own ways. Just maybe not in ways that people care about. The game will obviously have better multiplayer than Galaxy. The game is better looking than Galaxy. The game has better power-ups than Galaxy (since Galacy's power-ups were honestly some of the worst in the series). Depending on the type of platforming you prefer, the game could have better platforming than Galaxy. It could even be argued that the game has more content than Galaxy. A ton of levels, each with 3 green stars and a stamp, Captain Toad levels, mystery boxes, multiplayer, miiverse, and 5 different characters for single player.
Galaxy is a different template that some people might enjoy more. Some people might not care about multiplayer. Some people might prefer the way Galaxy controls, etc. And for some people, it will simply be difficult to match the pure joy they felt when playing Galaxy for the first time.
So there are plenty of ways this game has topped Galaxy and plenty of ways that it hasn't.