[msla]

Esperanto fails at being neutral because it's inherently oriented towards the subset of European languages Zamenhof based it off of. Someone who speaks German or Czech would have an easier time learning it than someone who speaks Mongolian or Korean or Mandarin Chinese.

[chillacy]

I find that spanish/italian speakers pick up esperanto the easiest, followed by I suppose french speakers and english speakers. Harder for any speakers who don't already speak a latin-derived language.