I actually ran the numbers on this recently, using Comichron's July statistics. I ignored #1s and event books, since we want to focus on stuff that's expected to attract and maintain a regular readership -- with a #1 you only have one data point, not a pattern, and events usually sell much better than regular books do just because you combine the audiences of each involved character.
I also ignored Star Wars stuff, since that's not really an apples to apples comparison -- especially considering Star Wars and Darth Vader sell better than any of their cape ongoings or limiteds, even Amazing Spider-Man.
What I found was that DC's median selling issue (Teen Titans) was selling better than anything outside Marvel's top quartile. The mean average of DC book sales is a little above Teen Titans as well. So the average DC book is selling better than the bottom 75% of Marvel's cape catalog.
Batman and All-Star Batman are selling better than Marvel's top ongoing, Amazing Spider-Man. Detective Comics is very narrowly behind Amazing Spider-Man. From there it's Peter Parker Spectacular Spider-Man, Flash, X-Men Gold, Justice League, Superman, X-Men Blue, Old Man Logan, Wonder Woman, Action Comics, Deadpool, and Harley Quinn, in that order. Harley Quinn is the highest book under 40k.
Marvel is in extremely real trouble.