One of my all time favorites are the two Shock movies, Shock and Shock 2: Latex, also Wicked Pictures makes pretty decent porn with alright storylines to them.
Yeah, you should check out http://www.wickedpictures.com/ . They focus on story lines with good looking stars. Unfortunately their sex quality is usually mediocre.
I wouldn't say "great storylines and plot" but if you like big budget historical porn then you should check out Private series from 8-15 years ago. Look into Tatiania trilogy, six part Virtualia, Pyramid trilogy. also Adamo Roma trilogy, Woodman Xcaliber trilogy.
A bunch of hot chicks are investigating the disappearance of a guy they all like (because he's the only guy in town who knows how to ass fuck good). They each follow a different lead but the guys who have the info they need won't talk. Not until they give up their ass, that is!!! Eventually they find out the guy was ********* by another hot chick who wants him all to herself. I'd tell you how it ends but don't want to spoil it!