Dh has always loved gaming, even back in the days of dial-up his phone bill was horrendous and he used to stay up til 4am playing online games and miss lectures the following day. When we moved in together I hated it and I hated the way the first thing he would do every morning and the last thing every night, was pull out the laptop and tap away at Championship Manager. We had many rows over it. I hated living with someone who was only physically present half the time.
We both started playing World of Warcraft, and that was worse. You had to commit 3-hour blocks of time 3 times a week to participate in some group events, and that required preparation in the form of hours more spent gathering the materials and researching the right combination of effective moves to take down a monster, as well as separate strategies for each one. I hated the time commitment though I loved the social aspect - some of my guild members are among my closest friends now. DH was/is very competitive so put way more time in than me, and I hated it.
Things came to a head after DS was born and DH managed to reach the top of his league in Star Craft II. He could never be interrupted, or spoken to. I took to taking a book over to the pub when the baby was sleeping, because if DS woke I would ALWAYS be expected to drop what I was doing, because he "couldn't" in case his rating dropped. Even on nights where I'd asked him to take over for me - he just wouldn't hear it. Eventually he realised that he just couldn't play something that required both a time commitment and uninterrupted time free from distractions, not with a small baby and a household to run. DH needs to be competitive, and hates doing something poorly, so it's all or nothing for strategy games.
(I think that since the advent of the smartphone I've got my own back to a certain extent - I'm frequently lost in Mumsnet, Wikipedia, my kindle app or doing my online Tesco shop!)
These days we still both play, but we play single-player campaign games like Witcher, Europa Universalis, Stellaris - stuff that you can log in to for a couple of hours, and then leave for a week or two if necessary, but no ratings or other teammates to worry about. And we try to give each other time to play, and split it evenly. Dh will do bedtimes and I'll get an evening in the week, or we'll give DS some screen time while DD naps over the weekend and he'll take Sat, I'll take Sunday. We also went from having 2 PCs to one, and that's made us split things a lot fairer with computer access.