I like ID4 probably the most ... it was so awesome at the time. I also like Signs, though I wont watch it as often as ID4 I just loved the build up where you didnt see an alien until like halfway through the movie and it was creepy.
I just watched "Monsters" this weekend, it wasnt nearly as bad as what I had read about it. In fact I like it , just didn't LOOOOOOOOOVE it.