I think the style is sometimes less important than being able to tell the story well. There are many different styles that I feel will pull me into a comic book as long as a perfunctory glance will tell me that the guy knows how to tell a story.

However, I do have a tendancy to want to see comics as being cartoons even if the style is more realistic like a Neal Adams or John Buscema (there is just enough in their style to skew it away from reality). The ultra-realism some artists go for (a Greg Land or Alex Ross) has a danger in my mind of being too static and failing to serve the story even if the art looks nice.

It seems like the "realism vs. cartoony" needle has shifted considerably in the past 10 years or so.

More and more artists are going for that ultra-realistic approach, like Gordon says. So what used to be considered realistic art now might be considered somewhere in the middle or even slightly cartoony.

I guess I prefer artists who have strong elements of realism, but still maintain that larger-than-life, dynamic feel that says "Superhero comic books." If I had to give it a label, I'd call it "believable" rather than "realistic." JB exemplifies this style, in my mind.