This question gets asked every couple of weeks on another forum I go to.
It's the same thing as auto detailing, it's not so much the products, but the process; a great photographer takes great photos, not the camera.
Honestly for anyone considering getting a DSLR you can't go wrong with either Canon or Nikon, hence I didn't vote in the poll, because 'best' is subjective. Both companies offer a huge selection of lenses and accessories. When I got my first DSLR a couple Canon junkies persuaded me to go with Canon, but either would have been fine. Only thing I would comment on is Canon does have an edge over Nikon regarding long telephoto lenses, which is why at big sporting events you see all white L glass, but theres a good chance if your an amateur you won't be able to afford any of those lenses as they are in the +2k range. Canon also has really good high ISO due to them using a CMOS chip vs the CCD chip Nikon uses. I did like the Nikon ergonomics better, but that's subjective, and I've grown accustomized to my little Rebel.
I can't say much about P+S as I have limited experience with them. If your considering getting a DSLR I'd go to a couple stores and actually hold them and go through the controls and menus to see what you like/dislike. Also look at the types of accessories and lenses they use to make sure they offer what you want and if it's financially feasible. Your buying into a 'system' more so then just a camera.