vote_for_palpatine said:

2

6

4

3

5

1

That is undoubtedly the correct order and not up for debate. I've thought about it extensively.

I entirely agree, vote_for_palpatine; although I like 3 and 4 equally, so in my ranking the position of those two is interchangeable. I also think that the director's cut of 1 is almost but not quite equal to 5.

I actually think 5 is underrated. Shatner actually did a pretty good job of directing it. It is just that the studio insisted on the insertion of much of the humor, and cut Shatner's budget more than once, so he had to change his vision for the film. Moreover, ILM were not available for the special effects.

The original film was to have been much darker and more interesting than the final result would suggest, and I quite enjoyed the novelisation of it. It is a shame the studio didn't allow Shatner to produce a director's cut like that of TMP. I also wonder if the original would have been better if Nimoy had executive produced it.