"so either the directors and studios were in it together on these movies (entirely likely I suppose: I don't know much about the movie industry; if anyone does

"so either the directors and studios were in it together on these movies (entirely likely I suppose: I don't know much about the movie industry; if anyone does know why this occurs, I'd be very interested), or one studio got wind of what the other was doing and made a "copy" before the original even came out, or else something much more subtle is going on." Or, they sit on similarly produced movies for years until such moment as it is economically "sensible" for them to release it. The entertainment industry has done that with dead people (Bernie Mac, Heath Ledger, Michael Jackson, etc.) for a long time. If they see advanced hype from one movie (in the case of Armageddon), they'll release their not-as-good one (Deep Impact, IMO) as an early-bird special to get people in the theater thinking "hey, it's just as good, whatever". Now, there are companies (like the Asylum) that make films _directly_ knocking off upcoming movies. They shoot and produce them in months and push it straight-to-disc for the rental/retail market. That's a different thing altogether.