Luigi Mansion 2 is a spin-off, New Super Mario Bros isn't.
New Super Mario Bros series is already lame, NSMB2 is just bad.
why is NSMB2 "just bad"? I thoroughly enjoyed it, personally. Super Mario 3D Land was fun too, especially the unlocked worlds after finishing the standard game. back to the New Super Mario Bros series: some of us who grew up on 2D platformers (namely: super mario brothers 1, 2 (the famicom version), the American "2" [enhanced port of Doki Doki Panic], and 3) still love the genre, and NSMB2 is a great way to enjoy similar mechanics, with updated graphics, and smooth framerate. also, when i showed my 4 year old - turning 5 in a few days - the NES super mario bros, he was asking why it looked like legos. lol. hard for kids who grew up with PS3, 3DS, Wii U, etc to get past the lack of animation and tiny sprite-based graphics of the 8-bit consoles. i have to admit we are spoiled these days, though. when i played the original super mario bros recently, I was surprised. i had forgotten how challenging the gameplay was back then.. the limitations of hardware were sort of a part of the overall game design, meaning the inherent difficulty in controlling a character precisely on those consoles, due to slowdowns, what looks like frame skipping, and other issues, was part of the experience.. you EXPECTED there to be x amount of delay between pressing "a" and the action occuring on screen, and had to strategize with that delay in mind...
it's like my boy playing some minions endless running (temple run style) game on his severely underpowered samsung galaxy kids tablet (galaxy tab 2 basically)... i watched in amazement as he took what felt unplayable to me, and learned to compensate for the lag by tapping in advance.. truly strange gameplay, but similar to what i grew up with, in some ways.
sorry for the diatribe.. lol