I realize this is an aging thread, but I just wanted to add my observation regarding SQ6:
Without SQ6, the Space Quest series would be complete. If the series had ended with SQV, then it would have ended on a good note, with Roger once again the prominent hero at the top of his game to seemingly live happily ever after...
...Until SQ6 came along, and:
Rendered all of Roger's greatest triumphs null. When the game opens, we're told that Roger's prior achievements don't matter.
Dropped a ton of new characters on us (Stellar, Circuit Syndey, etc.) who we're just to accept as having been close friends of Roger's, despite nothing having ever been mentioned about them previously.
Forced the idea of Stellar as a new love interest, which was unnecessary, since Roger had already "got the girl" in SQV.
Left us hanging at the end with the previous bullet point unresolved.
SQ6 is a disjointed mess, and lends nothing to the series. It just falls flat, and ruins an otherwise perfect series wrap-up that SQV offered.
SQ6 should never have been made.