Cameron's films are amazing. - It is clear that he is a talented director and his works are amazing.
But can this variant also mean that films from his video collection (by other directors) are good?
How can we clarify the difference between his works and his collection?
It would be highly unusual, in the context of discussing a director, to say "Cameron's films" and have it mean "his complete collection of Veggie Tales DVDs." Without further context, it would almost certainly be taken to mean "the films Cameron has directed."
For the other meaning, we would need to say something like you said; "his video collection."