They are nowhere near as good as the first one, but I've never hated myself for watching them either. I remember being really irritated with the 2nd one because it's almost completely a re-do of the first with a slightly different setting (airport instead of skyscraper), down to the obnoxious newscaster. I remember liking 3 quite a bit, mostly because of the interaction with Samuel L. Jackson, and the most recent one was an acceptable check-your-brain-at-the-door summer smash-bang-boom sort of thing.
That said, I don't think I've watched any of them more than once on TV and maybe once on video/DVD, whereas I can't count up how many times I've watched Die Hard.