Not really. I agree that Sting has written a lot of great pop music but he has also written some wonderful serious music too. And while we are talking about great composers how about some of the greats in the film world like Hans Zimmer for example. Don't see McCartney quite in that league. What about Frank Zappa, he was pretty good as well.
Oh and what about one of the greatest composers of our modern time. Chick Corea. Is McCartney writing as well as Chick. NOOOOOOOOOOOOOOOOOOOOO!
The more you think about it the more ridiculuos the OP seems to be IMO.