Why wasn't "DS9" "Star Trek?" What rule did it break that made it non-Trek and made "Enterprise" (God, I hate prequels) or "Star Trek: Voyager" Trek?
Mostly its darkness. A large part of what made 60s Star Trek a cult phenomenon was its optimism: "Things are bad now but we'll survive and they'll get better." DS9 has its triumphant moments, and its cuttingly dramatic moments, but it was never happy.
Another fundamental aspect of the difference is the way it developed Earth and the Federation. This started in late TNG, but perhaps only because they were working up to the DS9 premiere. One of Gene's first principles - you'll find it in The Making of Star Trek, Whitfield, 1968 - was never to go back to Earth, in aid of heightening the archetypal nature of the characters. DS9 was all about Earth's place in the universe, politically and spiritually. That's why Voyager was set seventy years' travel away; even Rick could see he'd wandered too far from the Vision.
Also it wasn't set on a ship. Even Voyager was set on a ship. DS9 really didn't feel like Star Trek to me at all till Sisko got a ship - and then he gave it to Worf.
Re: Moby Trek
Mostly its darkness. A large part of what made 60s Star Trek a cult phenomenon was its optimism: "Things are bad now but we'll survive and they'll get better." DS9 has its triumphant moments, and its cuttingly dramatic moments, but it was never happy.
Another fundamental aspect of the difference is the way it developed Earth and the Federation. This started in late TNG, but perhaps only because they were working up to the DS9 premiere. One of Gene's first principles - you'll find it in The Making of Star Trek, Whitfield, 1968 - was never to go back to Earth, in aid of heightening the archetypal nature of the characters. DS9 was all about Earth's place in the universe, politically and spiritually. That's why Voyager was set seventy years' travel away; even Rick could see he'd wandered too far from the Vision.
Also it wasn't set on a ship. Even Voyager was set on a ship. DS9 really didn't feel like Star Trek to me at all till Sisko got a ship - and then he gave it to Worf.