Battle Beyond the Stars was hardly horrible, it had quite a list of solid actors (George Peppard as a literal space cowboy!) and a pretty big budget for the time. Galactica 1980 wasn't even that bad. Apparently you haven't seen
bad sci-fi so I'll give you some advice:
What Reb Brown does for bad action films he double-does for bad sci-fi films. Have a look at Robowar sometime, which is quite literally a combination of terminator and Predator into some kind of dirty, italian gemstone full of ridiculousness. Even though IMDB lists it as action/adventure (and comedy for some stupid reason), it's as sci-fi as Terminator was if a humanoid robot walking around killing people is sci-fi.
Did you make a list somewhere?
No, but once upon a time I did reviews for a horror movie website under the name 'The Tallman'.
I can give you a quick short-list of things that will make your hair explode, though:
Lady Terminator (aka Pembalasan ratu pantai selatan). Hard to find but worth a watch if you can get it. Basically it's a mish-mash of Indonesian mythology and The Terminator, in that some hapless history student has a super-eel penetrate her vagina and it turns her into a killing machine. Complete with an almost line for line ripoff from the dance club scene in Terminator (ending in 'Come with me if you want to live!') it's one of those movies that drifts from hilarious to offensive and back again. It's not terribly 'scary' or 'gruesome', but it's interesting because it's so bad.
Barn of the Blood Llama. Now this one takes some doing to sit through, and I won't hold it against anyone who pussies out and shuts the movie off at the 25 minute mark. Basically some backwater hicks are genetically engineering the llamas and things go terribly wrong...that is, until some horny chicks arrive, their menstrual cycle being the only thing that stands between Earth and total Llama destruction. DVD version had some horribly made pre-movie 'adverts' to try and sell this as drive-in fodder.
Monsturd. Exactly as advertised, a SHITMAN named Schmitt 'reeks' havoc on the small town of Butte County, the creation of mad scientist Dr. Stern from Dutech (are you getting the crap-puns yet?). Aside from directors Rick Popko and Dan West (the two deputies) the acting is across-the-board horrible, to the point where Paul Wiener (the sheriff) looks like he's reading from cue cards at several points. Acting aside, there's a buttload of poop jokes and brown slime in this intentionally bad film. I don't know whether that disqualifies it but consider that Popko and West had the monster balls to actually make a sequel to this film called Retardead. Yeah, they did that.