People dismissing NSMB 2 probably missed that playing for coins in the other modes (or the normal mode) is a complete game changer in terms of how you progress and how the levels are built and offer challenge. I thought the game was way too safe until I started playing the other modes, then I saw what's really good about NSMB 2. It is a hard sell though.
People dissing the whole New series are just cray cray and can't see beyond art style. From multiplayer and massive improvements in level design as the series went on to the challenge mode and accessibility features like the bubble and super guide, these games always brought something important to the table and evolved the series.
NSMB2 had some of the best platforming i've played this gen.
i think the issue was it was more of a remix of NSMB Wii than a real sequel. which isn't a bad thing per se but not really expected with a "2" in the title