They are art. I mean, art is just something that is produced by human creativity. But whether or not they are high art is sorta hard to determine. You aren't going to see ad-agency produced stuff in museums anytime soon, but do we consider something like Warhol's soup cans to be a commercial? If we do, then that is an example of a commercial becoming high art. But if that pop art type of thing isn't considered a commercial, then I think we'd be hard pressed to find commercials as high art.

But that's now. Maybe in 100 years our commercials will be exhibited in art exhibits in the same was that old penny-dreadfuls are sometimes considered literary now.