Good game single-player but when multiplayer comes into the equation...
Pros:
-Controls are responsive with only small problems (when instead of picking up a barrel to throw at an enemy you might accidentally pick up a friend and throw them)
-Over 60 levels!
-Just plain fun
Cons:
-Graphics, they aren't bad but they could be better.
-Nothing new to the table except multiplayer and 2 suits
-No point of star coins (all you get for getting them ALL in one world is an extra stage, also you can buy videos with them which is kind of cool)
Notes:
-Really hard, but in a good way most of the time but sometimes frustrating!
-Multiplayer is fun if your not serious about it.
I can safely say you should go out and buy New Super Mario Bros. Wii but I know some people won't like the game because of the difficulty but don't worry there's something that's called a super guide where Luigi beats the level for you after 8 deaths!
And if you are wondering if it would be still worth it if you don't have 2 wiimotes, don't worry it's just as fun singleplayer!
I could go on about how great this game is but that would take to long so as always whether you buy it, rent it, or pass it's up to YOU!