Personally, I prefer artists who can convey great movement and action. I find guys like Land, Liefeld, and even Jim Lee are all artists whose style is very stiff. Alex Ross falls into this category, too, because his style feels more like photographs. Though I do like Ross.
Some of my favourite artists tend to use a minimalistic, yet dynamic style: Sean Phillips, Darwyn Cooke, Cameron Stewart, Scott Kolins, David Aja, Michael Lark, John Cassaday, and of course, Jack Kirby. I don't need realistic art and in fact, I think the closer to realistic, the less dynamic the action looks. One exception to this is Bryan Hitch, whose style works really well for action.
I can't stand when a page is either too busy or the characters are overdesigned - a sin which most of the original Image artists have a problem with. Even though I'm not an artist, I believe in a similar rule about wrestling: don't do once what you're not willing to do every day for the rest of your life. I don't think a lot of artists realize just how stupidly complicated their designs can look, especially guys like Lee or Liefeld. The reason a lot of the classic costumes work is because they're simple and sleek in their design. There was absolutely no need to add stupid yellow streaks going through Flash's costume, for example, or V-neck armour for Superman. Or goddamn dog collars on Wonder Woman and Green Lantern (Kyle Rayner's costume before Hal returned). Or the overuse of single or double page spreads. Sometimes, just a well-placed panel works so much better than spreads, which I feel should only be used for big moments where you need to see a larger picture.
I also think certain artists work much better with certain writers. Grant Morrison seems to bring out the best in Frank Quitely (and vice versa). Warren Ellis brings out the best of the John Cassaday. And best example of all, Jeph Loeb brings the best out of Tim Sale (and vice versa). In fact, I don't know any work of Tim Sale's that I enjoyed even remotely as much as his work with Loeb.
All that said, I also think certain artists are needed for certain stories. I also really like Jeff Lemire's work, but it's not a style for, say, superheroes. It works best for character-driven stories like Essex County or Sweet Tooth. Same as Tony Harris on his Starman work. They're not artists suited well for a lot of action.