Funny, I'd say that L.A. is "underrated". The appearances are often disappointing, but I think few places pack so many hidden treasures. It's just that from its drab appearance, the treasures are hard to find even by locals. I think of the city as a glorious car wreck of cultures, geology, nationalities, and identities.
Overrated- Washington D.C., it's run-down and downright shabby once you go away from the tourist sites and the Mall.