Yeah 4 in all, and yes i strongly disliked them. Not my cup of tea at all, of course that day stuck in my mind so I instantly thought of it when the question was posed but I'm sure I could think of tons more crappy films.
Looks like there's another one coming out this year and a sixth in development: http://en.wikipedia.org/wiki/Underworld_%28film_series%29#Underworld:_Next_Generation_.282015.29
