Damnation alley is not even the worst Sci-Fi movie ever made
This is far from a great film but I'll take it over any CGI affair being produced today. It has a fun cast (Peppard, Vincent and Haley); a super score, one of Goldmith's best; and economically savy and cool special effects. With that said, here are some choices (off the top of my head) for the worst Sci-Fi films of all time:
1)Planet of the Apes (the remake)
2)Quintet
3)Rollerball (the remake)