If you rely on mind-altering substances to unlock your creativity, maybe you were never that creative in the first place? Personally, I don't really see the difference between taking steroids to boost performance and taking LSD to boost performance. I don't see why one is cheating and the other makes you a misunderstood genius.
A question, though: If you found a painting to be beautiful and loved it, but later found out that the artist was high when he painted it, would you not find it beautiful anymore or not love it?
(Also because I think the distinction matters. Sports involves competition. Not all art does. If a person enters an art contest and is using drugs to make their artwork better, I would consider that cheating. If they're just doing something for fun? It's other things, but not cheating.)
A painting's aesthetic quality has nothing to do with the subject at hand IMO. My question then would be whether the artist could still have created something that beautiful without the drug; it wouldn't effect how beautiful the painting was, but it would effect my opinion of the artist. I have more respect for the artist than can create of their own volition, through work and practice and training, than someone who relies on chemicals to achieve what they want. It may enhance something in the person that is already present, but isn't that exactly what a steroid does?
I can see what you mean about the competition angle though.