Satires are a delicate beast. They have to walk a fine line between capturing the original story and lampooning their subject with well crafted humor that is pertinent to the source. Sadly, in the realm of horror comedies, this fine art was mostly thrown to the wayside a long time ago.
I'll be upfront and honest here; I've never seen the source material that "Vampires Suck" has sunk it's teeth into. I don't have any intentions to watch the "Twilight" films any time soon, either, so there is a chance that some of the humor here is completely lost on me.