Firm believer that either you have it, or you don't. College taught me enough practical knowledge that I could get a foot in the door. Most of my REAL education has been through work.
BTW, you do not have to be a great artist to be a good designer (and vice versa). I can't draw well at all. Don't get me wrong, I can sketch and doodle when needed but compared to some of my friends who are true artists, I don't compare. One of my good friends and coworkers is a great illustrator... but he can't put together a composition to save his life. So I definitely think there are multiple skill sets withing "Graphic Design" and you don't necessarily have to be good at all of them.