Christopher Hitchens famously said that the four most overrated things in life were champagne, lobster, anal sex and picnics. I'm with him on three of those. Nobody will ever improve on Hitch's list, but I'll nominate four things as next-most-overrated: falafel, the Bay Area, brownstones, and diners.
Falafel. People get so happy when they see a falafel place, or when there's falafel in the lunch buffet. I wouldn't feed falafel to a farm animal. It's dry and mealy on the inside, hard and greasy on the outside. I was a vegetarian for 11 years, and during that time I fooled myself into thinking that a lot of vegetarian things were good, but I was never deluded enough to like falafel. Most things that are overrated are pretty good in absolute terms, but falafel isn't just overrated—it's terrible.
The Bay Area. Having lived in the Bay Area, having visited many times, my opinion is that living in the Bay Area would be very nice as long as you could walk to the Cheeseboard, walk to your job every day, and never be forced to listen to Bay Area residents talking about how great it is to live in the Bay Area. In reality, living there means you will be listening to a lot of that, and you will be spending a lot of time in your car. Everything in the Bay Area shuts down too early at night. There is too little world-class high culture. Also, many Californians are just too laid-back to have the manners that my Southern and Midwestern heritages have conditioned me to expect from well raised people. You don't need to tell me about the ocean, the mountains, and the rest—I agree that stuff is great. I also think that my friends who live in California have seen no more of it in the past couple of years than I have.
Brownstones. Not enough window light, no view, and no building amenities. Frequently devoid of their original charm thanks to "renovation." Yet brownstones cost millions of dollars! I wouldn't buy a brownstone if I could. You are literally buying a facade.
Diners. I know diners. I was raised in my parents' diner. I'm never more comfortable than when I'm lolling in the booth of a diner. But there is way too much romance about diners. New York diners in particular are an expensive way to eat terrible food. Being on a quest for the great American diner—which, to be clear, I often am—just goes to show how worthless most diners are. You don't go on a quest for something unless it's elusive.
Bonus overrated thing:
Your favorite TV show. I agree that we're in "the golden age of TV." However, that's basically like saying we're in the golden age of burritos. Which we are! But burritos, like your favorite TV show, are overrated.