If you drill down a bit that ,make little sense. Course differ and it depends on fit.
I have certainly heard the head of English at an academic school argue that UCL has a stronger English Department. If you want to study Mathematical Economics most would agree that LSE offer a more rigorous course than Cambridge. Imperial definitely has the edge on a number of engineering degrees (EEE, Biomedical, etc), partly because they offer early specialisation and partly because some areas of research are London based. There are also plenty of subjects that Oxbridge does not offer, yet London, because it is so large, can. For example Imperial and the Royal College of Art work together to offer courses in Innovation and Design Engineering.
But I agree. MN in particular, is very Oxbridge focused. With Bristol and Durham often being considered next best.