If you have several million pounds, you can have a nice life literally anywhere. For the same money, you'd have a better quality of life outside London.
Theatre: London is certainly better than the provinces, if you like that kind of thing. I don't.
Sports: neither spectator nor participation sports are a London speciality.
Clubs: if that means nightclubs, Manchester had a much better club-scene than London when I lived there (mid 90s). I'm too old for clubbing now!
Museums and architecture: people visit museums and gawp at architecture when they're visiting a place. Once you've seen a museum, you've seen it. Sure, it's pleasant to live among nice buildings; but most of the London cityscape is not anything I'd call architecture.
I lived in Central London for 20 years. I hated it for 17 of those years. It takes an hour to get across town on the (stinking) underground, which is the quickest way. Traffic is the most-aggressive of any place that I've driven in the UK. People are unfriendly; nobody lives in London to make friends, they live in London to make money. Everyone's in a hurry, presumably because they want to make a lot of money so they can leave.
I find that people are much more friendly in London (they are certainly a lot less racist in general, which is lovely). It's the premier city in Europe, and very international which is lovely.
It has such a great mix of things – you are constantly surrounded by history and there is always something going on.