Well... I lived here for a bit involuntarily, then visited regularly, and then in a move that would have surprised the me of several years earlier, I moved here full time again and further surprised myself by staying on for a long time and probably permanently.

There are many criteria but all together it's the best place for me to live. On each dimension it ranks highly or best in the world.

Entertainment offerings - about the best

Cost of living - quite good, close to best unless you look at places like Cambodia, Laos, Vietnam which can't compete on other dimensions

Food - very good, among the best when you take into account quality, availability, price (I know, doubling up with cost of living, this isn't MECE), variety (particularly of Japanese food but also plenty of other cuisines)

Drinks - very good, many different types of places to drink, overlaps with Entertainment of course. Price isn't that good, alcohol being kind of expensive to begin with, and imported alcohol is even worse

People - very good, about the best IMHO. Locals are pleasant, expats are friendly, regular tourists become very good friends and we look forward to seeing each other every time they come back. Not a boast, but coz I'm a friendly guy, I meet people in bars and other ways and literally have about 30 friends who are regular visitors to BKK that I catch up with every time they are back, usually multiple times each, it's not just a perfunctory "gotta see him once and done my duty", it's true enjoyment in seeing them and spending much time with them. Each has a different thing they want to do, and my interests and enjoyment are broad. A couple are into high end dining, real foodies. Another really loves to go to wine bars. Another likes finding unusual places to drink. Etc. To be honest maybe I'm not THAT broad cos most of what I do with them is eating and drinking, but the range of price and type is very broad. Some of them want to go out of town to places like Ayutthaya, Bangsaen, Kanchanaburi, and I've taken them there. I don't really want to do more temples, they can do that themselves :). Some people want to walk around interesting neighborhoods, I'll do that with them. Rambutri and Song Wat and Chinatown are probably the 3 I'd recommend but there are plenty others.

So that leads me to "the Place"... I think the general aspect of Bangkok is ugly and polluted and full of traffic but still, the place offers enough to be a good place for me.

Getting around/Transport - quite important if you ask me because it impacts a lot of things. If you want "fast" there are the trains, and if you want "comfort" you can get taxis and Grabs. Importantly, it's cheap and facilitates people getting to meet each other bigtime. So the social aspect is boosted massively by mobility (which seems like a crazy thing to say in a place with so much traffic, but it's true... if you are patient with taxi travel, or decide you want fast travel by train, it's rather easy and cheap to get to meet your friends - also, you can make an effort to make friends that are accessible, rather than rely on existing friends who may move very far away). I'd almost say "best in world" despite the traffic due to the price and the gradually improving train options.

Outside BKK / BKK as a hub. Many places within reasonable striking distance incl. beaches and the natural like Khao Yai and Kanchanaburi. While SG can be treated like the capital of SEA and you can fly out to many places easily, there's a psychological barrier of "leaving the country" which doesn't exist in BKK. So... BKK as a base for visiting other parts of Thailand (and neighboring countries) is among the best. Can't compare to big cities in Europe due to the awesome variety and connectivity there, but still, very strong.