I'm not sure about the best but when it comes to art (concept mostly) I would recommend Seneca college and their Art fundamentals course. It isn't designed specifically for game design but it teaches a lot of art based skills on tight deadlines. Also Art fundamentals offers classes in photoshop as well and it's only one year for about $5,000-CAD.
They also have a game course and traditional animation course but I can't vouch for their value. I just know that Seneca makes some phenomenal artists.