Honestly, I never found Spaceballs all that great. I felt it was too much a parody of Star Wars specifically. True, Galaxy Quest has a lot of Star Trek parallels, but it's really a more general parody of SFTV from the '60s through the '80s. Alexander Dane owes more to Barry Morse of Space: 1999 than to Leonard Nimoy, and Dr. Lazarus kind of reminds me of Hawk from Buck Rogers. Tawny Madison owes as much to Galactica's Athena as to Uhura, and the idea of a token character whose main job is to repeat the computer's words is reminiscent of David Kano from 1999. The cheesy puppet-and-wirework effects suggest the Irwin Allen shows or some of the less successful effects in 1999, and the precocious preteen kid in the crew suggests Will Robinson from Lost in Space and Doctor Zee from Galactica 1980. So it's all in there, and that makes it feel more universal to me, not so specifically derived from a single thing.
Plus, of course, the movie isn't just a parody, since the characters have real substance and there's a real story there.
Plus, of course, the movie isn't just a parody, since the characters have real substance and there's a real story there.