This is my opinion, I can't be certain, but my experience is that native English speakers use a much larger lexicon of words in their everyday language than a native Spanish/etc speaker.
I don't know about everyday language, but English definitely does have a massive vocabulary compared to most contemporary languages. Through the centuries, languages have been getting simpler, but English is the odd one out. It's constant borrowing of words over the last thousand years or so has made it comparable to far more ancient languages in complexity.
"There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.