First of all Chicago, Illinoizzz, let's show some respect: it's cheesesteak, not cheese steak. Okay, got that off my chest.
I too spend a fair amount of time in Philadelphia having lived out east as a kid and still with lots of family in the city and suburban area. And I agree with FrankP that Monti's serves a better cheesesteak than any of the heavyweights in Philadelphia. The reason is pretty simple - much better quality beef. But they also make sure to serve the cheesesteaks on fresh Amoroso rolls (not so simple in Chicago) and I think they've now gotten the beef, cheese, onion ratio just right.
Although white American cheese would not normally be my cheese of choice on any sandwich, it works extremely well on the cheesesteak and in my opinion, creates the perfect balance on the sandwich. I'm also a big fan of the Rocky, but beware it's peppery punch - they don't call it the Rocky for nothing.
But aside from the cheesesteak, I'm also a big fan of their Italian Hoagies (sub that is, but I grew up calling it a hoagie too). A very respectable sub, with just the right ratio of meat to cheese to onions (and again served on Amoroso rolls). And I also enjoy their fries seasoned with celery salt - much better than it sounds. Beyond the obvious, Monti's also has daily specials, usually soups, and they've made some pretty damn good ones. And for those of you that haven't tried Tastykake, they carry them here. My personal favorite is the Butterscotch Krimpet.
Aside from the food, these are really nice people running Monti's and they've also succeeded in hiring really nice people. Whether you're a regular or a newbie, you'll be treated like a regular. And whether you just want to pick up something to go after work, take your kids for a meal, or go in the evening to watch a game and grab a few beers, Monti's is a great choice. I'm thrilled to have Monti's in Lincoln Square, and more than happy to support it for a GNR.