Giggs suggested in an interview that the two Manchester heavyweights will be fighting it out for glory.
Quinn admits City are favourites for the title but says none of last season's top six should be ruled out.
"That was a load of c**p there he just said about United and City winning the title wasn't it," Quinn said on talkSPORT.
"He just totally disregarded Spurs, Liverpool, Arsenal, Chelsea, Everton. Well Everton won't win the title, that's a gimme.
"I think City are favourites aren't they, I think City are favourites.
"Look, they're going to improve under Pep Guardiola but they were far from the finished product last season.
"You saw flaws in their defence, you saw a guy that tested every system last year Pep Guardiola, to peak for this year.
"They've got some exciting young players as well."
Later Quinn backtracked on his Man City claim and said there is not one team who are clear favourites.
"I think it's wide open last year, it really is wide open," he added.
"I don't think you can pinpoint any favourite at the moment."
