Some are better, many are not. There are not many other systems of the same scale as London's in the continent, and those that are aren't really much better. The Paris Metro for example is very dirty and smelly in my experience, although the trains are frequent which is nice. Generally, across the world, I find larger cities have dirtier public transport, with the exception of Tokyo which is spotless. There are lots of cute and beautiful tiny systems across Europe, like Prague, but it's obviously easier to make a small system that works well than something at the scale of London, Paris or NYC.
Where London really struggles, as the whole of the UK does, is the awful ticketing system. That said if you don't care too much about the cost and stick to the Oyster zone, you can just tap your phone and not think about it beyond that. Oh, also the lack of AC for the few weeks of hot temperatures we get, but that at least is apparently being fixed soon.
Functionality wise, I've never had any issues in London. The open data is accurate and comprehensive, so the app of your choice has accurate route planning, you pay by tapping your phone and follow the instructions. Other systems have mostly caught up now, but for a long time London did better than 90% of other systems in that area.
I'd say the city I found most surprisingly good was Stockholm. Very comprehensive for the relatively small population size, and all the stations were beautiful and clean. If anything, it seemed overbuilt and almost desolate a lot of the time. I'm not sure how they afford or justify the upkeep on it given that most other systems in the world seem to be struggling.
> Some public transport absolutely is 24/7.
It may well be, but Zurich's isn't, which is what I was talking about! Very few places have 24/7 trains, but Zurich doesn't even have 24 hour busses except at the weekend.