I believe Roger Ebert, among others, has championed the idea of 48fps for decades now to no avail. My problem with altering the 24fps of film is that it would look more and more like hd/digi acquired images. In feature films, shooting/projecting 35mm at 60 fps would look more like HD than it would film and that would not really be a good thing imho. If I'm shooting film, it's because I want the image to look like a film and 24 fps is a big part of that. Gaining more data (high fps) in motion pictures is not my goal...if it was I would go with a high end digi camera for that crisp hi-def vid look. Not to mention shooting at a double or higher fps would cost A LOT MORE DOUGH which takes the option right off the table for almost everyone.
Chris, you are definitely not the first one to take this issue up. In theory it makes sense, but like anything else, the market just does what the market wants irrespective of theoretical "better" ways of production. So in the end, you can certainly do whatever it is you want to do...so if YOU have a lot of cash and YOU want to shot 120 fps, go for it bro!