Sex: Something you can only have if you're not some ugly looking pile of shit. You can't always have it. Sometimes you or your partner is not in the mood for it. Sometimes it's that time of the month. Sometimes One of you are sick. You can only do it a few times per day on average. It makes you tired. Doing it when it is hot just makes the heat worst. It's not something you can do if you have visitors over. It's not something you can do anywhere. There is some risk to it aka making someone preggers.
Games: Everyone can play them. You can always play, even if you are at work it is easy to hide. If someone is not in the mood to play with you online there are plenty of people you can play with instead and it would not be called cheating. There is no time of the month where games suck. If you are sick you don't have to worry about making your computer sick. You can play all day just fine. It rarely makes you tired unless you play for days without rest. Playing games when it is hot does not make it hotter. You can play games while visitors are over and you can even play with them. You can play games pretty much everywhere. Even if you screw your computer, I doubt it would get pregnant.
So with that said, why would anyone pick sex over games? The only people who would do that are virgins who don't know jack shit about sex and the problems that come with it.