Revenge is sweet. Sweets are not healthy for us, but they taste so darn good. That's why we watch so many revenge movies, which feel so wonderfully delicious.
In the movies, you can see many examples of characters fighting to get what they want. There are just as many examples of one character exerting power over another; that's what every trial lawyer occasionally dreams of: bending another to our will. In the movies, it's satisfying to see a fight end with a clear victor, or a conflict with one person clearly imposing his or her powerful will.