Just to get the typical disclaimer out of the way, an authentic cheesesteak is made with Cheez Whiz. It tastes better. It doesn't necessarily taste more natural, just better.
Pat's (and Geno's) are definitely tourist traps, but it doesn't mean their steaks aren't any good. Both are excellent.
I have not been to Sam's, but if a hound is looking for an excellent example, any of the Papa Jake's fit the bill. Excellent cheese fries as well.