I like Gulo's, but it's been a while since I had it. I used to live in Buffalo Grove, so Gulo's and Joe's were two of the main places I'd order from to get thin pizza.
Gulo's actually moved across the parking lot to a slightly bigger location. Many years ago I bought 4 pizzas from Gulo's and 4 pizzas from Joe's and my family had a pizza taste test. I think Gulo's won overall, but I can't remember. Joe's is very greasy, but that imparts flavor (it certainly looks like they use whole milk cheese) not just "grease." Joe's is also a somewhat dingy restaurant. You'll know what I mean when you go there. They put the pizza in a bag, not a box (which is annoying), but it's really old school. Look at their old menus on the wall.
Bottom line - Both are worth checking out if you love really thin, tavern style pizza.