I don't know. I much preferred NSMB2 over SM3DL. Then again, I largely do not like 3D Mario games.
However, I do agree with the consensus here. If you weren't a fan of NSMB or NSMBW, this will not convert you. It's much easier than its predecessors and doesn't bring a whole lot of "new" to the table. At $40, your money would be better spent elsewhere. If you got this at a much lower price point, I'd say consider it then.
I don't feel I wasted my $40 because I actually love 2D Mario games and I've thoroughly enjoyed NSMB2. In fact, I'm playing through the game for the second time now because I've already earned all five shiny stars on my first save and I'm nowhere close to 1,000,000 coins yet.
Unlike MarioMan, I won't sit here and say ERMAHGERD!! NU SUPUHR MURIOH BRUHS TUH IZ TEH BEST GAEM EVUR!!!, because I do recognize the game's flaws. Flawed or not, I liked it. But, that's me.
Trust the masses here. Most of them are saying the same thing. It's a good platformer, but is rather sub par for a Mario title. Keep your $40 for now.
Currently Playing: Ultimate MvC3 (PS3), Mario Kart 7 (3DS), LoZ: Skyward Sword (Wii), SFxT (PS3), Mass Effect 2 (PS3), Hyperdimension Neptunia (PS3).