I definitely prefer the first 5 album covers. They're iconic, colorful, and all around original. Plus the style and execution was outstanding - not sure if they were hand-painted, but they give the impression that they were.
The latter 5 album covers were ok - the Loads have the whole artistic statement thing going on which is cool, and they're definitely colorful and striking. I can't stand the St. Anger cover, too comic book-looking. DM had a cool concept, but poor execution - looked half-assed and too plain for me. I like HTSD, again cool concept but the white background is getting old.