I was born and raised in the suburbs of Philly.
Thin sliced ribeye is the best meat, IMO. The choice of cheese is up for debate, but I prefer provolone. I like grilled onions on mine, as well. That's what I grew up eating.
The key is to get a good roll, and make it soft on the inside and crispy on the outside. Ameroso rolls are the best, but unless you want to pay big bucks to have it FedEx'd to you, get what you can get, and toast it until it is soft on the inside, and crispy on the outside.
The finished product should be a meaty, savory, cheesy sandwich on a roll that has a crunchy crust.