There is indeed an extremely small corner of non-amateur couples porn (*krhm* Lelu Love's videos *krhm*) where the way people have sex, the mood and intimacy in it actually somewhat resembles something that might happen in real relationships, but.. a full-length porn movie with solid character development and actual, well-written plot? Something that would compare in any way to a really good book or a good non-porn movie?
Forget it. Doesn't exist. It's useless and hopeless to even try to request any porn site for something like this. They don't have anyone capable of writing anything better than they already do. Amateurs on the other hand do not have the production facilities that it would require.
When you take away the plot and character development requirements: vivthomas, joymii and x-art might have something that would pass as a couples-friendly porn movie.
Edit: Hmm. Some retro porn as well, but I can't remember any at the moment. That's actually something that I should look into further. I haven't watched those nearly as much as I should have.