My current favorite is Jean-Léon Gérôme. Though I have vague memories of seeing his work while I was in college, 16-20 years ago, I have recently rediscovered him and his awesomeness. I almost wish I actually were a time-travelling super-villain so I could hop back a hundred years, conquer France, and spare him from being executed like most of his fellows.
Here’s the first paragraph of the Wikipedia article about him:
More importantly, here’s the Wikicommons page dedicated to him I’m particularly fond of Painting Breathes Life into Sculpture (currently adorning my desktop), but there are many other lovely images there. Be warned, though, that some of these paintings contain nudity.
Anyway, that’s just me. I’m sure others hereabouts have opinions on which artists are worth praising.