Have you had this question on the G.B.C. before? Which city is the best city in the world to live?
I have been preparing people for this test since 2011, and about 99% of my students always have the same answer: Tokyo. I love Tokyo too, but no-one has been able to convince me that it is the best city in the world. Why? Because the answers are always the same. Tokyo is the best city in the world because it is convenient and safe.
When lists of the world's best cities are published, Tokyo rarely makes it into the top 20. And the cities that do aren't there just because they are convenient and safe. Usually cities are ranked according to a combination of economics, infrastructure, politics, quality of life and the natural environment. If you ignore these factors, you risk sounding ignorant.
So, if you want to argue that Tokyo is the best city in the world to live, you might say something like this:
I think Tokyo is great. For me, a good city is a good place to live, and I think that there are three aspects to good quality of life: work, leisure and convenience.
When it comes to quality of life, Tokyo is unparalleled. We have some of the best restaurants in the world; we have lots of parks and places to relax; and we are the modern cultural center of Asia. When people talk about the greatest cities in the world, they always say, "London, Paris, Rome, New York and Tokyo", and not without good reason.
But, you know, more than just being a fun place to live, a good city also needs to give its residents chances to work, and Tokyo is the commercial center of Japan and home to some of the world's largest companies. Furthermore, the sheer size of the city means that Tokyo-ites have vast economic opportunities, the likes of which many cities can only dream of.
Mind you, lots of jobs and a booming economy can only happen if you have good infrastructure, and furthermore, leisure activities are not relaxing if it takes you hours to get there. Tokyo is incredibly efficient and convenient for its size. It has the best train system in the world. You can get anything you want or need, and we are also connected closely to Asia, North America, Europe and the rest of the world. I know that convenience is not really glamorous, but when you live in a city with tens of millions of other people, it really helps!
I could go on, but I honestly feel that Tokyo offers everything you need for a great city.
This answer is good, because it limits the scope to my personal opinion ("For me, ...). It also touches on a couple of more worldly metrics for greatness (economics and quality of life. There are good links between paragraphs and topics ("More than being a fun place to live" and "jobs... can only happen if..."). And it puts convenience in context and explains why it is so important in a city like Tokyo. In the end, your answer is your own, and you can use whatever ideas you think are appropriate. Just make sure you back it up with some sound reasoning!
If you are interested in one ranking of the best cities of 2017, read this article: The 23 cities with the best quality of life in the world.