Oh, the voice is really Shatner. In fact they had the entire TOS cast for those two games! They were disk-based games on the Amiga, and PC. But then they did CD-Rom editions where they hired the cast to do voice work the re-releases. There was going to be a third game with the original cast, but unfortunately Deforest Kelly died, and it fell through. For years I was unable to play them again, but then some brilliant son of a bitch invented Dosbox.

