I grew up in Philly and made a point of trying all the famous cheese steak joints. I think Jackson House has them all beat. The bread is trucked in fresh daily from South Philly, and the meat and toppings are just incredibly tasty and succulent. I usually go for the cheese steak hoagie, and I never ever regret it. Another favorite of mine is the Manhattan burger, with Swiss, slaw, and Russian dressing. I've had bites of friends' hoagies there too, and they are consistently excellent. I have not yet tried the roast pork sandwich (another Philly classic) but I feel I have to one of these days. I just know it's going to be good.
Make sure to try the birch beer while you're there. It's delicious, and I usually avoid sugary sodas, it's really a big treat.
I love the cheese fries here. I usually share an order.
The line can be long and seating can be difficult to find at peak times. Hours are limited, so plan ahead. But it is so worth it.