My first reaction is to say "both". But when I'm forced to give an answer, I say "better".
Gene Roddenberry WAS a genious when he invented the basic core concepts of Star Trek. His vision was indeed great.
But whenever he had too much control over the details of production and storytelling, the results weren't as good as when other great minds filled his original vision with life.
Iirc, the beginning and some episodes of TOS, TMP and TNG season 1 was when Roddenberry had the strongest influence on the production, and those are imo among the weaker parts of the franchise.
Some amazing ideas that became iconic were introduced by others, wasn't i.e. much of the Vulcan culture contributed by Dorothee C. Fontana? Also, TNG became better the less Roddenberry was involved.
Maybe this relates a bit to how I view George Lukas' involvement with Star Wars -- the original idea in 1977 was lightning in a bottle. But the prequels imo proved that Lukas had no idea whatsoever WHY the original had been so amazing.