So think about this. People often think that their city is the best in several different ways. Wherever they live has the greatest bars, the most beautiful women, the best tacos, whatever.
But how do people come to hold these opinions? Well, one way would be to try to remember the best members of the category in question that the person has ever experienced, remember which city each was experienced in, and note that most or all are from their own city. The problem here is that, even if there are no differences in quality between cities, any person is going to have experienced more in the city they are from. So chances are that the top 10 will mostly be populated by things from their own city, regardless of actual quality differences.
For example, if I've had 100 tacos in my home town of London, 5 tacos in Toronto, and 5 tacos in New York, chances are my top 10 tacos will mostly be from London even if New York truly has, on average, the best tacos.
This may seem obvious. But there is one surprising consequence: this also applies when you substitute "worst" for "best" in the above reasoning. Thinking of the bottom 10 will lead one to their own city more often than not. So, paradoxically, I bet most people would say that their own city has both the best of the best and the worst of the worst, depending on how you ask it. "The worst tacos? Well, I got really sick after that one at Taco Bell in London, so London has the worst tacos." "The best tacos? Well, Si Senor in London has great tacos, so I guess London has the best tacos."
I bet that if you surveyed people from a given city, asking half of them about the worst city for any given thing, and half of them about the best city for the same thing, both groups would choose their home town the most. Yet another example of how people are dumb and their brains betray them.