At the risk of sounding political.... Rocky 4 was basically a film that was made to be an anti-Soviet propaganda piece. Whole film was that the evil Soviet Boxer can fall to an American. Basically the same Reagan era stuff I don't wanna get into.Rocky (after the third, shouyld have skipped over 4 & 5 and gone straight to Rocky Balboa)
http://en.wikipedia.org/wiki/Roger_rabbit#PrequelI feel the same way about Roger Rabbit, but as I understand it, Robert Zemeckis is trying to get a sequel green-lighted.
The idea of a sequel/prequel was around for some time... I really think that War plot line had some bite to it (I wonder if that was true or a rumor). But there was a second book Who p-p-p-p-p-p-p-plugged Roger Rabbit that was a very loose sequel to the movie.
I really doubt this movie will happen, though. Severely.