Maybe it's one's ability to recognize a plot hole but not let it ruin the movie for you? I'll admit that it's annoying when a character does something stupidly complex when a more simple solution is right before them, or when a writer uses an implausible solution like hacking an alien space ship computer with a laptop, a la Independence Day. I can shrug it off, though, as a bad choice or lazy writing and still enjoy the rest of the movie. I've watched Fifth Element a dozen times and love the interaction between Bruce Willis and Milla Jovovich (who is totally hot in that movie) but I can see how Chris Tucker's and Gary Oldman's characters can push the movie into 'bad' territory.
I might be one of the few that sat all the way through Plan 9 From Outer Space but I think Backaroo Bonzai was just plain bad.
For the record I'm with you Eppie. I like a lot of those movies too, and I don't think they're necessarily bad. I'm pretty forgiving of occasional potholes or inconsistencies. I don't think everything has to be airtight and perfect to be fun and enjoyable. Chris Tucker was ridiculous, but TFE still has some great acting, great moments, great action and good special effects. It does a lot of things very well. I also think Starship Troopers is a lot smarter than it appears on the surface. It's a satire and I think the story is cool, the plot makes sense, the special effects are really good for the time and the action is over the top and well done.
A true SBIG fails at almost everything. Even the technical aspects. Stuff like out of focus shots, boom mics and camera reflections in shots, bad sound, bad music, bad ADR... and that does exclude a lot of traditionally cheesy, "bad" movies, and the ones that do it on purpose. A lot of the movies mentioned so far are actually shot well and scripted with tongue firmly in cheek.
*PS, I thought Plan 9 was pretty entertaining and falls well within SBIG. There's something done badly in almost every single scene, lol.