This is one of my very favorite episodes, and I've always wondered what a Star Trek with Captain Pike would have been like. It has excitement, suspense, and even a thinking plot. It definitely works much better as a stand-alone episode than it does as a backdrop for "The Menagerie". In that capacity, it is used as a flashback to propel a very odd story where Spock commandeers the Enterprise to deliver a badly injured Pike to what appears to be a morally bankrupt race so he can live out an illusion of a normal life. Very un-Spock like IMHO.
That said, it seems apparent to me that Gene Roddenberry lifted some very obvious plot ideas for this pilot from the Twilight Zone episode "People Are Alike All Over". He even borrowed actress Susan Oliver who appeared in that episode in a similar role and a with a similar name ("Teenya" vs "Vina").