Love Wagner's music. Where would we be without the classic "Kill the Wabbit" Bugs Bunny episode? For a brass player, Wagner is right up there as one of the more fun orchestral composers.
I never saw the big deal about Van Gogh until seeing a piece in person. Then it was "WOW! NOW I get it." Amazing stuff.
I used to work with a guy who was an absolutely brilliant engineer (for those of you who remember typewriters, he was one of the people who brought us the the IBM with the "ball" instead of individual keys.) He was also an amazing artist--sculpture, paint, you name it. Living proof that you can be both technical and artistic. He decided to paint miniatures, entered an international competition, and took second place. He was throughly disgusted--his opinion was that given the short amount of time he'd been doing miniatures there were flaws in his work, and if he won an award the judges obviously didn't know what they were doing, so he didn't enter any more competitions. He was also a lyricist--his most well known piece was only a children's song, but covered by Burl Ives, Rafi, Danny Kaye, and others. I was lucky enough to have him for a mentor for about 6 months. He might not have been in the same class as a Van Gogh or a Wagner, but had the most amazing mind of anyone I've ever met. He didn't seem to be too difficult to get along with, although he didn't suffer fools gladly. One of the best compliments I've ever received was when he told me "You're one of the few people I can tolerate."
For some of the great artists, it must be (have been) incredibly difficult to see or hear the world in strange or beautiful ways that are/were so obvious to them, and not have anyone with the same understanding/perspective to discuss it with. Think about how frustrating it is to talk knives with someone who tosses them in the dishwasher and sees nothing wrong with it--and imagine what it would be like if everyone else was like that. If someone is out at the extreme limits of ability, it must seem like no one understands what you're doing or has any sense. Enough to drive one to be antisocial and develop some drug/alchohol issues.