Super Mario 3D Land walks all over the Galaxy games. It's not even close. The only thing that could make 3D World better is if Nintendo added online multiplayer, which they won't, but a girl can dream.
EDIT: My mistake. Let me play as Daisy. I don't care if I have to beat the game three times. I'll do it.
I'd love to play as Daisy and/or Walugi in a game. Those are my top two Mario Kart/Party/sports characters.
I've yet to play Super Mario Galaxy 2 so my current stance could change. But I finally got all 242 stars in Super Mario Galaxy last month and I agree that 3D Land is far superior. The more I keep seeing people praise that game, the more and more I keep getting the urge to unleash a massive wall of text pointing out the amount of flaws, derivativeness and sparseness.
That said, while I am still playing 3D Land currently and going through the special worlds, I still don't think it is close to Mario Sunshine or even Mario 64. For me, Sunshine still reigns supreme as the pinnacle of 3D Mario and even that game isn't perfect.
I just suddenly thought about Sunshine in HD graphics. That thing would probably look super amazing for a Mario game and you could probably tell the difference more than the fantasy abstract lands of this 3D World game.