To answer this question, we must first come to an agreement about what makes one wrestling style "superior" to another. Since i made the claim that i consider it superior, i'm going to explain what i meant by it in this context. I believe Greco-Roman Wrestling is superior because in my opinion, the techniques it focuses on are the most essential and important techniques of grappling and focusing exclusively on them leads to a more refined skill in those techniques for the practicioners of that style. Another reason i consider it superior is that i consider it superior entertainment, that is, more pleasant to look than other styles.
This is my issue with freestyle. Greco techniques are, in my opinion, the core fundamentals of grappling. The more lax ruleset of freestyle wrestling waters it down, at least from my anecdotal experience. While freestyle wrestlers i knew had almost always difficulty transitioning to greco, as they felt their entire skillset was castrated, the greco wrestlers i knew transitioning to freestyle felt freestyle was much easier for them than even greco.