I see it as a graph, which I can hopefully make with ASCII.
. E ^ y
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< | > x
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\/ . A
. C
The x-axis represents entertainment value (right is more, left is less), and the y-axis represents how well the movie achieves its intended effect (up is more, down is less).
Point A is Plan 9 from Outer Space. Intended to be a serious drama/social commentary, the horrible acting and production values make it impossible to evoke any seriousness. In so doing, it becomes one of the greatest comedies ever.
Point B, Future War, may actually have worse production values and acting than Plan 9, bolstered by the lack of any coherence in the plot (In the words of Mike Nelson, it's more like movie loaf: parts of real movie, chunked and formed), and becomes the funniest failure at a real movie I've seen so far. However, it didn't fail in its purpose as much as Plan 9 did: the producer remarked on set that he hoped the movie would show up on MST3K, and so, while their hopes of creating a watchable, profitable action flick were not to be, at least one intended effect was.
Point C is 'Manos' The Hands of Fate. Hal Warren meant to show that a fertilizer salesman with $19,000 could make a profitable horror film. He was successful up until the word "could." It made no money, had no horror, and led Hal Warren to kill himself. This time, the ludicrously poor production values (such as all the lines being dubbed in by the same two people) can't save the movie from itself, and even with the MST3K crew riffing it, it becomes difficult to stay awake.
However, 'Manos' only brought us to 0 entertainment. Point D, Home Alone 4, takes us deep into the negatives, as do most crappy attempts at comedy. This one, however, loses even more points for completely disgracing a good comedy. Rather than just failing at making you like it, it seems to be intentionally trying to make you hate it. If that was the intended effect, then they did a great job, but assuming that their purpose was to make a movie deserving of the Home Alone name, they failed horribly. This makes Home Alone 3 look like Shawshank (as opposed to feeling like being in the actual Shawshank prison, which would be a relief compared to HA4).
Finally, Point E is Hobgoblins. This film's intended purpose seems to be to make the sleaziest, basest, stupidest rip-off of Gremlins ever, with plenty of celebrations of sluttiness and shallowness thrown in to boot. That was a rousing success (no pun intended), and because of this, it is one of the most unwatchable films ever.
This should actually be a 3D graph, where the Z-axis represents the amount of meta-entertainment. (i.e., the Land Before Time films aren't entertaining in and of themselves, but the fact that there's over a dozen of them is.)