This is a very controversial subject; opinions vary and there is no consensus. As you can see if you peruse past discussions on the subject, such as:
It's worth noting that there are two primary styles of deep-dish pizza. There is the single-crust "pizza in the pan" whose best, most well-known, and most conveniently-located places include Lou Malnati's, Pizano's, Gino's East, and the original locations of Pizzeria Uno and Pizzeria Due. And there is the double-crust "stuffed" pizza served by Giordano's, Edwardo's, Bacino's, and Nancy's. If you've never had either one - and non-Chicago locations of Uno's Chicago Grill don't count - I would start with the original single-crust pizza in the pan; if you've already tried that and you want something different, give stuffed pizza a shot.
Wherever you go, you can phone ahead with your pizza order to avoid waiting 30-45 minutes while seated for it to bake. Deep-dish pizza is usually eaten with a knife and fork. And the recommendations on the menus for sizing are accurate. (Visitors from out of town are often surprised to hear that 3-4 people can feel absolutely stuffed after sharing a large pizza, but it's true.)
Personally, I think that Lou Malnati's has the best deep dish, hands down. While they have lots of chicago area chains they haven't sold out to the rest of the country and stay true to their food, service and ambience. Food is great, service is good (definitely call ahead like nsxtasy recommended) and ambience is completely mediocre, which doesn't matter, because you are there for the fabulous pizza.
i agree. i order malnati's frozen online (i live in ny) and its still very good. another one i really like when i am in chicago is the original due's on ontario. a "small" special will feed two and the drinks at the bar are strong and real reasonable. also that garbage salad they serve is outstanding . i was very disappointed in ginos east the last time i was there a few months ago. it seemed like they lost the recipe for how to make that cornmeal-based crust.
Is the Lou Malnati's on North Wells St a good one? That's the area where we'll probably be for lunch. Don't think we'll be able to order a pizza ahead of time, but we don't mind waiting a bit and soaking in the atmosphere either. Can't wait to get my hands on some deep dish za!