Well, it was designed by an almost entirely different group of people, was it not? It may be different but it still has its charm.
I did say it may not be fair to compare them. Still, Super Mario Galaxy was charming in its own way. I don't know, the New Super Mario Bros. games just seem to be lacking something. It's an identity crisis of sorts. It's trying to hearken back to the good ol' days while also trying to be its own thing, but it excels at neither.
I agree with your comments about the DS version, but have a hard time understanding what your mean about the Wii game. New Super Mario Bros Wii fixes the mistakes of the DS game and improves on it in every level. While NSMBDS was lacking at parts, NSMBW is classic Mario in every way possible.
NSMBW is like a better version of the DS game, but still has plenty to improve upon. Bros. 3 and World are near perfect games. They make the most out of the new mechanics (i.e. leaf, feather/Yoshi respectively). SMB3 had some useless/underused power-ups like the hammer bros. suit and the frog suit, but I'm pretty sure you could get the leaf in every level (the Tanooki Suit being a cool but glorified leaf power-up). Not so in NSMBW. While there was almost always something to discover by having a leaf or feather/Yoshi, many levels don't reward you for exploring with a new power-up in the New games. It's a thin line, I know, but something I feel the old games have over the NSMBDS/W.
Also, NSMBW loses points for no classic controller support. Sideways Wii remote works well for the most part, but sometimes I accidentally hit the A button and shaking the Wii remote slightly during normal play has led to a few unintentional deaths. More lazy programming on Nintendo's part. Inexcusable at this point, really, considering games like Smash Bros. Brawl employ every possible controller option. A very good game, but I feel there is still much room for improvement.