I'm claiming 4. Although, I've only really explored New York and Montreal. I was in the mountains just outside of L.A. , and all around it, but I never actually went into the city. I've been through Chicago, but didn't really spend any time there.
I would recommend Montreal to anyone. I've been there twice, both times for a few days for a pearl jam concert. I had a blast! It was a bit of culture shock, I'm sure, but both times left me buzzing for a few weeks afterwards. It was hard to settle back in to my normal life, I'd go back in a heartbeat.