The second one (Matrix Reloaded *SPOILERS ABOUND* thread) is probably the more archive-worthy because it goes deep into all sorts of possible theroies and interpretations of the movie. Looking at them again, I think we could keep just it and then Matrix Reloaded would be well represented (whereas if you had one in there, you'd be getting short-changed).
The third is interesting, as you say, but I don't know, the trilogy went belly up, so I'm less likely to wanna see a Revolutions post at all, especially a highly abstract one. Similar feeling about four.