I got the chance to play this game at MCM London Comic Con this October, and it was a brilliant experience.
Super Mario 3d World brings the free-roaming aspect to the Super Mario franchise in a glorious way. Not only does it have one of the best multiplayers I've seen in a Nintendo first-party game for a while, Peach is actually a playable character. Oh, and there are cat suits too!
The levels within the game are well designed and relatively easy to navigate, as well as having see-through pipes to climb around in- Mario's a real plumber now!
One of my favorite aspects of the game is the multiplayer, allowing for up to 4 players at the same time. You can save up bells (these make you wear cat suits) and other bonuses to use later, meaning that you can stop yourself dying or allow yourself to climb up walls. The character selection is quite strong too, and the teamwork aspect really makes this game something special.
I think this game is definitely a brilliant addition to the Super Mario franchise. I have to say, things have really improved since New! Super Mario Bros (the last Super Mario game I played). Keep this up Nintendo!