Last night, I watched "Der Untergang", a subtitled German film about the fall of the Third Reich, from the perspective of Hitler and those around him at the end. It had one of those Downfall videos in the middle of it. Perhaps this could have been entitled "Hitler discovers that his generals don't have enough men or materiel to obey his orders, and that he's going to lose the war".
Not that funny, as you can see.
Frivolity aside, this is an amazing and powerful film. The reason why the parodies are so funny is that Bruno Ganz's Hitler is played with a passion and rage (not to mention detachment from reality) that is entirely plausible as a reaction to the destruction of his dreams of world domination. It is of course hilariously over the top as a reaction to the relegation of Sheffield United, or to being told off for ending a sentence with a preposition. Note - both these links are rather sweary, so perhaps not safe for work.
The parodies are funny, no doubt about it, but you should also consider spending the 2.5 hours to watch the actual movie. It's really very very good.