Good is subjective, but we may choose particular traits to define "good" for us and rank based on this. For instance, if lots of different ways of expressing yourself, including lots of synonyms with subtle nuances distinguishing them is part of what you consider good, than English is a wonderful language. If logical rules that are followed pretty uniformly, leading, perhaps, to greater ease of learning are what you prefer, then you may prefer Spanish. If "purity" in comparison to an earlier version of a language is valuable to you, then my understanding is British English is not for you, but southern/appalachian American English is.
I find that claim the upper class British accent is "unaccented" absurd. I can imagine two meaningful definitions of "unaccented," neither of which applies. "Unaccented" could refer to an accent that is such a subtle blend of accents that it is not distinctive to any single region. This, as I understand it, is what most national (US) television programming strives for. Alternatively, "unaccented" could refer to least changed, in which case we're back to Appalachian English.