A movie needs to understand it's place in order to be good. Movies like "Freddy vs Jason" can get away with gratuitous plot holes because they're campy. Nobody goes to "Freddy vs Jason" expecting a riveting plot.

Movies like "Underworld" however sell themselves as being serious and should be taken seriously. So, when a movie like that has cruise liner sized plot holes, it kills the entire experience.

This is just one example, however. If you're gonna be campy, be campy. But if you're going to be serious, then for the love of God don't glaze over things like "plot" and "character interaction."