I know Pit Bulls are extremely popular in my area BUT, you don't see them often.
Some year's ago one Pit Bull owner was allowing his Pit Bull to roam free at our youth football practices...and the dog was NOT people compatible. He was reported and I have no idea what happened but the pit bull never showed up again at the practices.
I think I can say around here the most popular breed are Chihuahuas. At least... they are roaming the streets of town at all times... (not out where I live in the country).