I'm not a huge fan of the New (Wii) series. It's focused on four player co-op and because everyone bumps into each other, that collision has to be taken into account which makes the platforming more forgiving and simpler with wider platforms and more padding to fit all of them in on-screen comfortably. That's okay and decent fun in that situation with other player characters all bopping around, wall-kicking, and bubbling up, but when you're playing by yourself, the accommodation in design proves to just be too much damage to the more traditionally-focused single-player design seen in older Marios. Tight level design and more demanding obstacles and enemy placements and behaviors are more fun because the skill needed to get past them is much higher allowing you to get more satisfaction from the process of mastery. With just a single character on-screen to worry about, the game doesn't have to be overflowing with opportunities to save yourself from a bad bounce or misjudged landing and generally means you have to focus to maintain that zen state of control discipline that makes Mario intense.
I don't think the New series is dead, but I really want a big new 2D Mario with the sensibility of the classics. Until then, 3D Mario is the only one I look forward to now.