I don't have a definitive favourite, but off the top of my head: Cheung, Chiang, Alex Ross, Hitch, the late Michael Turner, Jim Lee, Ditko, Byrne, Aja, Amanda Conner, Manapul, Quitely.... and many many others.
And as ashamed as I am to admit; I like Greg Land's earlier work *ducks behind cover*
Depends on the character. Some folks draw one character well, and another not so well. One guy that I think does everyone well is Alex Ross. I was a big fan of McFarlane in his early "weird panel breakdown" days, and when he drew Hulk. Neal Adams was very well-rounded also.