From a tourist's perspective (been to Philly like 4 times) and I find myself constantly eating when I visit, I slightly prefer Geno's over Pat's. I can see how locals or those who frequent the Big 2 places find them a bit overrated. But when you live in the midwest and all you have are mall eatery cheese steaks, there's nothing like a visit to Philly. Hell, I once got a cheese steak at a gas station in Philly and it was fantastic...it really is all about the hoagie roll.
Last visit, I ate 2 Geno's and 1 Pat's in a sitting, and if I had to cast a vote, it would be for Geno's. Also, the last time I had Jim's, I found it way too dry. I've never tried Tony Luke's.
On a different note, Lorenzo and Sons pizza is hands down my favorite pie of all time.