I mostly enjoy trying to figure out what comes next. Great acting is a bonus as I see it. It's nice to have it, but plot and writing is the key. Take the movie
Brick which arguably has some lousy acting. I still enjoyed it greatly. Of course it is an homage to my favorite film (Miller's Crossing), so I'm biased.
For a counter example, the contrast between A Fish Called Wanda and Fierce Creatures was stark. It takes more than the same actors to make it a win.
Don't get me wrong there are some really impressive performances out there that some movies wouldn't be the same without. The Lion in Winter, for example. I guess I mostly see it as analogous to nutrition: bad enough and it can screw anything up, but once you get above "good" levels, there's diminishing returns.
I think a lot of experiencing any film or music is set and setting. Seeing a plotless action flick with your friends can be a lot of fun. I still hum music from the Katamari Damacy soundtrack just because I loved the game so much. If I had come across it independently I wouldn't have given it the time of day.