Like others have said, I feel like I have to balance what are expectations and resources with what the end result is. I mean, I've said it before but as incompetent as
Manos is, I have more respect for it than I have for something like
Transformers because the former was made by an inexperienced man with an inexperienced crew in a shoestring budget, whereas the latter was made by a big studio with gazillions of dollars, and still made my head hurt and ache for a week.
I also can't fault something like
Birdemic or
Sharknado because they are achieving precisely what they set out to do, so

On the other hand, these cheap schlocky Asylum-like films have become such a big thing, that they've jumped the shark themselves. When something like
Sharknado came out, it was like thinking "Whoa, wait a minute? Sharks and tornadoes?! tee-hee!!" But as they keep churning more and more of these absurd shark-hybrid films, the novelty wears off and you're left with mostly a dullfest with a giggly title, if at all.
On a similar vein to the above,
The Human Centipede 3 is one of the worst films I've seen. Not because it is about multiple people being sewn mouth-to-anus, but because it manages to even make that dull and boring. For what it's worth, I think the first one is legitimately good, or as good as a film about a mad doctor sewing people mouth-to-anus can be.
Battlefield Earth is a good example, though, where you get some of the most incompetent filmmaking mixed with an actor's ego with disastrous results.
A Good Day to Die Hard is another terrible film, mostly because it takes a character we used to love and turns it into a dull mockery.
The League of Extraordinary Gentlemen is another example of big resources and big stars, all wasted in a mess of incompetence, awful writing, and bad CGI.
I have a weird triumvirate of films on my list of "worsts" that tie together Eddie Murphy and Robert De Niro, mostly because despite the talent involved, they are lifeless dullfests:
15 Minutes,
Showtime, and
Holy Man. I saw the last two in theaters and they still rank among my worst moviegoing experiences.