Quality of life comes down to personal preference. I'm not sure there's anywhere else I could live (at least without having to learn another language) and not feel any need to own or use a car, the pub theatre scene is probably the best in the world (likewise the museum collections), a huge range of musical performances, and it's the best place to find people for specialised hobbies (netrunner in my case, again literally the best place in the world for it in terms of the community size). Of course other places have their own selling points, but London has a lot going for it if you like that sort of thing.