I recently sold about twenty of my dvds, including two televsion box sets....and I didn't really have that many to begin with. I have a new rule now that if I'm not going to watch it more than once, I don't buy it. Anything I owned that I watched only once I got rid of. My tastes also changed from when I first started buying dvds.
If I remember right, I got rid of Matrix, Matrix Reloaded, Animatrix, Terminator 2, Timeline, Mary Shelley's Frankenstein, Fast and the Furious, and a quite a few others I don't remember.
I still have some I'm thinking about selling.