I don't think they're overrated but I do feel the idea that only good Cheesesteaks exist in Philly is overblown. Any restaurant, any city, in any state could make a Cheesesteak just as good, if not better than Philadelphia itself.
Also, the idea that it has to be Cheese Whiz is exaggerated too; some of the best Cheesesteaks are made with deli-cut American cheese, sometimes other types of cheeses as well.
I think the Chi-town Italian Beef sandwich is more overrated than any other mainstream regional sandwich, imo. I've seen people brag and boast about it so much, but it looks like a basic steak and peppers on a roll dipped in meat juices reminiscent of French Dip minus the peppers. I'm sure it tastes good, but to me, that ain't nothing to brag about.