The danger of "more" is that it dilutes the purpose and voice of the original. "Cowboy Bebop" fits in this same realm, I think. It had a single season. They did a movie. They said everything they needed to say and left it at that.
Firefly is an interesting example of that. If it had not been cancelled so quickly, would anybody remember it these days? A lot of shows start out strong and then completely fall apart.
It wasn't so bad that I couldn't wait to stop watching it but... it wasn't good enough that I couldn't help but finish it. I still want to finish it...
