I dunno about you, but I think this has that same special 'Mario feeling' that the first couple of Marios had.
Honestly, based on what I have played so far, it really is every bit as good as those games. I can see myself coming back to this game over and over again, and just playing it for fun. Something I can't say for too many games these days.
Maybe the later stages aren't as fun? Who knows. But so far,
1)I've been challenged by it. I've died many times so far.
2)It's fun.
3)The stages don't seem that short to me.
4)The addition of the wall-jump, the butt stomp, and the triple jump make the game much more fun.
5) most of the classic sound effects are there. Except for Star-Man's theme, which I think is the N64 version.
6) Graphically, it's not a big turn-off, like so many griped about prior to it's release. Would I have preferred handdrawn? Sure. Heck, in my perfect world, it wouldn't look much better than the NES Mario 3, graphically(though I'm sure I'm alone in that department!

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I'm Really enjoying it.
I'm not surprised that a few aren't experiencing the same old magic they had when they were kids. Those are very special feelings, those growing years. When you're young, everything seems much more awesome or special than it really is. That's not to take anything away from the classic Marios, of course. Those games are utterly brilliant, wether you're young or old. But for a lot of people, they expect this game to re-create those old feelings. But anybody who goes to play this and expects anything other than a really, REALLY good game, is setting themselves up for disappointment.