Between the huge numbers of impressionable kids who would enjoy just about any positive new experience & the nostalgic adults that remember these games fondly (many of whom have/will soon have children of their own), there's a massive potential market for games that fit the mold of the classics mentioned in this thread. I don't think their success would come down to whether "Xbox gamers" are inherently interested in them or not, or whether gamers in general have lost their capacity to appreciate whimsical characters/scenarios over deadly serious ones. The main factor would be (as always) whether there was a decent advertising push behind them.
There are plenty of quality indie/small development team-created platformers on non-Nintendo consoles that do about as well as can be expected given the general public's limited awareness of them, but in the AAA market only games with large opportunities for low-cost revenue generation after the initial sale will be favored by publishers. It's no accident that most top-selling titles (again, other than on Nintendo systems) these days are the ones with the most aggressive DLC strategy.
A standalone, story-based platformer simply won't normally lend itself to a high take rate for additional content. Sure, you can create new levels/characters or whatever; but they tend to either be limited to some sort of challenge mode, or basically a re-skinned/shorter version of the original game. Anything on the level of adding new mechanics that could break the existing framework and you may as well just fill out the length a bit & sell it as a full-priced sequel instead. Compare that to primarily multiplayer-oriented games which offer a high degree of motivation to keep up with the competition and the path to maximizing profit looks to lead in the opposite direction from an "Old School" game.
New technology needs more expensive games to showcase it - unfortunately consumer demand for the next big thing has the potential to drive out entire genres that don't promote new tech as effectively. Just like in the movie industry, income from blockbusters may help artistic passion projects reach a wider audience in a roundabout way, but studios know where their bread is buttered. They need spectacle to draw attention. On the other hand, I think that fans of platformers have a particularly keen understanding of the devil being in the details - while graphics & story certainly matter, it's the responsiveness and feel of the running & jumping that make a game worth playing. I mean, a tale as simple as "Our princess is in another castle," moved over 40 million units! When I think of these games, I don't recall caring about the motivation for my actions (even the 7-year-old me thought the plot of SMB was absurd); I recall instead how each physical interaction felt, how each new level/enemy/environment changed the rules ever so slightly and taught me new skills/tactics in a way that felt natural, progressive and most importantly, fun. I'm pretty sure that's something every gamer can relate to in some way.
