I haven't read Dan Brown but I would place Morrison at a much higher level of skill and talent as a writer, given the differences between their respective fields.

I imagine the point of the comparison is that both are seen as taking complex ideas and treating them in a cavalier or even superficial manner. Perhaps there's something to that: I remember reading somewhere that Morrison has always admitted to being "cheerfully shallow" when it comes to picking up whatever ideas or concepts happen to catch his eye for use in his stories.

However: 1) I think his use of those ideas is often quite deft and seamless; 2) his treatment of theme and character is, at his best, orders of magnitude more profound and insightful than pretty much any comics writer this side of Alan Moore and a very few others (maybe Ennis and Ellis); and 3) he really is a first rate word-smith in a way I don't believe even his biggest fans would claim Dan Brown will ever be.

The Grant Morrison/Dan Brown comparison for me is not a comparison of ability to write prose, but that both Morrison and Brown are (or were in Brown's case) looked at as inventive geniuses for their wild, bold ideas in their stories, when really all both were doing is acting as a tour guide through other people's ideas presenting them in stories they called their own and drinking in the accolades which should have gone to the other people who actually came up with the ideas.

-M