I'm a Johnny-Come-Lately to Roadfood.com, but I was just lookin' at this particular thread, and noticed that the Cheez-Whiz vs. Provolone that WestsideTommy brought up...
Here's the thing - and I'm with you on the fries, although I gotta be honest, I think Al's Beef sucks... Johnny's out by Harlem and North Ave is still the best... even if it is (just barely) in the 'burbs... but that's another debate entirely

...
Oh yea, The Cheez-Whiz thing... CheezWhiz, while something that no one in Chicago (being only an hour away from "America's Dairyland" (as the Cheeseheads call it) would normally consider something to eat - let alone as a quintessential part of a local delicacy - is a must on Philly Cheesesteaks, and I'll tell ya why:
The meat juices fuze with the oil in Cheez-Whiz (Canola oil is like the first or second ingredient in that stuff) creating a natural condiment so that you don't have to add anything. Kinda like the gravy on a beef... except, as you and I both know, beef gravy has a lot more flavor for the sandwich than the juices alone on Philly's sandwich.
Philly's Best on Belmont (by Clark) is actually alright, and it is owned by some Philadephia guys who know a thing or two about it... go check it out and see what I mean. Yea, you'll have to venture over to the North Side, but it's cheaper than flying back to Philly to see what I mean.