Out of the entertainment categories you just listed (porn, movies, music, books, games, sports) I think the porn can have the worst side effects on your life because it directly interfere with a relationship with your partner (many people go for porn rather then for sex with partner) or can demotivate one from searching for real relationships because porn is easier. And that can ultimately lead to worsening one's quality of life.
Do you have any credible, not thoroughly debunked research on this? I don't think anecdotes would be helpful here since most couples I know regularly commission porn of their characters and seem quite happy together.
Oh this actually brings up a whole other can of juicy worms: Forced monogamy.
Almost every culture guilts people into remaining in unsuccessful relationships and makes people feel like a failure if they have to break off a relationship.
