Deep dish pizza DOES suck when you have it at a place that tries to imitate great pizza places in Chicago.
Lou Malnati's - absolutely superb deep dish. They use hand-crushed San Marzano tomatoes for the sauce, and the pizza is sweet, light, with a heavenly crunchy crust. It's a special destination and my family eats there every time we're in town.
Giordano’s - Go here if you're VERY hungry. They make a pizza "pie" that's made with a fan-fried garlic butter crust, cheese, another layer of crust, and then "toppings" (sausage, onion, and mushroom mandatory), then crushed tomatoes on top. Unique and amazing flavor. One pizza will feed 4-5 people. Go to the original location on the South side for the best experience (those old seasoned ovens make a difference).
Pequod's - Rustic deliciousness. Smaller deep pizzas with the edges burned "just right" so you get that caramelized cheese taste. This pizza was created to have with a pitcher of beer.
Any other city I've had deep dish pizza has been a heavy, rich mess. They don't use the right pans to get the crust right, it's mostly crust and to filling, it's undercooked, it's so dense it's overcooked...runs the gambit.
For those hating on deep dish pizza, knowing the history of it may help put you in the proper mindset: deep dish pizzas came from an Italian family recipe for "Easter Pie," where they would make a large pie full of special ingredients for guests during the holiday meal. It's supposed to be a special occasion food that that they turned into business.
Anytime they take a specialty food away from its origin, it loses something.