The very first line of English Wikipedia's entry on Esperanto proudly informs us that the name of the language is pronounced /ˌɛspəˈræntoʊ/ (and reinforces that using two common notations and an "alternative" which does not come much closer, really). In my opinion it couldn't be wronger. This is, surely, how an English speaker would read it if they knew nothing of the language, but why would it be necessary to spell it out then? For an Esperanto speaker this would be approximated perhaps by "Es-prenĉoŭ" which feels mildly insulting, as a non-attempt at even trying*. If someone told me they spoke es-prenĉoŭ I would be tempted to doubt the fact.
The non-trivial information here that would be appropriate to list in an encyclopædic entry should be how it is actually pronounced, which is something more like /ˌɛspɛˈrɑnto/ or /ˌɛspɛˈranto/ to my best knowledge. Why list anything at all if not this? I would put it in but
- I'm not that well-versed in IPA,
- I think there may actually be some reason why it is like this. After all it was very likely someone who knows the language that put it there.