Striker Mario said:
I think it deserves its praise for its solid gameplay and deserves criticism for being retreads that sit way too closely with nostalgia. That being said, New Super Mario Bros. is my favorite Mario platforming series, though, because I grew up with them, simply. I grew up with those character voice effects, for instance, and it feels very jarring that the older games lack those, something I can't really get used to. Even in Super Mario Bros. X, I wish for addition of voice effects. I also grew up with wall jumping, ground-pounding, multitudes of powerups, triple jumps, and probably the New Super Mario Bros. soundtrack, which I don't find any more forgettable than Super Mario Bros. 3's soundtrack or worse than Super Mario World's soundtrack.
There is also modding those games, but that's a different story and it's not really fair to rate New Super Mario Bros. highly for that because it wasn't intended to be modded. But it still stands, I am confident that Newer Super Mario Bros. may change your perspective of what kind of potential New Super Mario Bros. games have and it'll probably spoil you too. Just as long as you look past the somewhat sleepy soundtrack (I changed it myself, but it made me love the mod probably more than if I didn't change it) and the world map designs (though it's because the team's modelers weren't available).
I think this clarifies why I'm a bit alien about part of the comments on this thread: I grew up at the end of the NES/SNES era (where the Koopalings were naturally part of the cast, even in other media) and followed the Mario games and franchise until the GBA/GCN era, then the university and the need to focus on other aspects of life made me skip the Wii/DS era. I came back in the Wii U era only because I won a Wii U at the end of 2013. When I bought MK8, the interest in the Koopalings (that, remember, were featured in M&L:SS so I pretty much left with them and Bowser Jr., although the last Mario game I had at the time was PM:TTYD) rose again and in fact I'm here because of Mario Kart first, and then because of the Koopalings (I really liked the
Koopalings#Family_relationship section that thoroughly expalined that my friends and I weren't visionary nor victims of bad translations at the time with the Koopalings being Bowser's children).
Actually, my interest in the NSMB series grew because of the Koopalings, as remember, I had skipped it completely and frankly, its presentation - even in the naming! - was so uninspiring I wouldn't have touched it until much later if it wasn't for them.
So, yes, part of the complaints here about the Koopalings are alien to me, like for real

.
Regarding the games I played (NSMBW and NSMBU, I have yet to begin NSMB seriously), I think they do what they are meant to do, offering a gameplay and a simplicity similar to that of the older games while offering some important modern additions (physics, moveset, simultaneous multiplayer and so on). They don't seem to have the aim of being as groundbreaking as SMB, SMB3, SMW and SM64 were at the time (I was in most of that time!). And quite frankly, even SM3DW doesn't seem to have that aim, in my opinion. I think the last game that legitimately had that aim was Super Mario Galaxy.
This does not make them bad games, though, I now find them neat (well Dry Bowser isn't very neat especially since Bowser fell in the lava many times before and nothing happened while NSMB had that Super Metroidesque cutscene at the end of the first boss, but you get the point...), with a decent difficulty level - except for the a-bit-dreadful 9-7 in NSMBW - not to say that NSMBU even tried having some decent not-too-generic backgrounds, and since now the main series Mario games rightfully don't use most of the classic cast - no problem with that, as long as we have interesting characters and species like King Bob-Omb, Dorrie, Petey Piranha, the rabbits, Piantas, Lokis, Tanukis, Plessie, the Toad Brigade with Captain Toad, the penguins, Gobblegut, Rosalina, Pom Pom, the Hisstocrats and indirectly, Wingo and Draggadon coming out of them - it's nice to see Mario platform games with the classic cast - but really, give some stamina to the Koopalings, they are painfully easy since SMB3!