I tend to be on the old fashioned side. I'd have to say Richard Serra would top that list. It's funny, what was once controversial ends up mainstream(think of punk rock lol).
Koons, imho is all hype. But he is good at hype...the whole NY scene is all about marketing personalities.
Damien Hurst, again imho hype.
I could get into a huge debate over the current/post modern art world but it would fill up hours of our time lol! In general, I tend to like art/images with lasting visual value over images/ideas dealing with political messages or shock value.
My belief is that "visual art" has lost a lot of it's original "visual" attributes. Conceptual art has basically taken precedence over the visual aspects.
I think that ultimately if one purchases a work of art for ones abode, then it must be something worthy of looking at for years to come(I'm sounding like Buffett lol....."of permanent value"). The contemporary art world is basically made up of artists making works for "thinkers" rather than viewers. Well, it's more complex than that.
My wife is telling me she has some lunch ready! Gotta go for now. I'll get back on this issue, it's a tough one.