Generally speaking--with few exceptions--I'm not a big fan of the painted cover on a comic book. It's usually too austere and seems to deny the fact that beyond the cover there is a comic book inside. I like comic covers to look like actual comic book art with black line work, dynamic action scenes, captions, dialogue balloons--the works.
One exception to this rule I make are the painted covers on the old Gold Key TARZAN comics--though I admit this is mainly nostalgia. Another exception would be the cover for LIMITED COLLECTORS' EDITION No. C-31 (October-November '74). I was thrilled when this tabloid-sized comic arrived in the mail and I pulled it out of the crush-proof mailer. There on the cover was the painting of Superman by H.J. Ward with colours by Sol Harrison--a reasonable facsimile of the painting that hung in the DC offices for many years dating back to the early '40s.