Which is best: Original (with original soundtrack) - 1974
Re-Release (with generic soundtrack) - 2000
Remake - 2014
I vote for the original 1974 movie. To me the original sound track goes perfectly with the amateur nature of the production. That is not meant to be derogatory in any way because the charm of the story and the movie lies in the fact that an amateur on a shoestring budget was able to create something so campy and cool with no "big stars" whatsoever.
If you've never seen the movie with the original soundtrack, this channel has cleaned up versions of all the songs and lots of other interesting stuff:
What about other remakes, better or worse than original?