I'm a teacher and have done masses of research into the effects of computer games on primary aged children as part of my Masters degree in education. Using technology in education was also the topic of my main dissertation.
There are MANY benefits to gaming for young children. I'm not going to go too in depth because I could write pages, but they are highly beneficial used correctly. They build confidence, literacy and numeracy skills, reasoning, problem solving, fine motor skills, reaction times, dexterity and are bloody brilliant for encouraging reluctant readers. There is also a social aspect to them if children are able to play with an adult (sustained shared thinking) or their friends.
Obviously you need to make sure that parental controls are activated and online safety advice is heeded. You don't have to have Xbox friends, you don't have to play online, you don't have to have interaction with other people.
My DD has used an Xbox since she was 3, in particular games like Minecraft and the Portal series. She also enjoys more "play" type Nintendo games like Mario, Animal Crossing and Professor Layton. She was able to use simple coding apps on the iPad at 2. She's now really proficient in age appropriate coding.
ICT is now cross curricular. Children use technology through all aspects of education - I really don't understand those who are reluctant to use iPads, games and other tech with children. It's part of life now. A balance is recommended of course.
As for time spent, start as you mean to go on. My DD9 is allowed an hour screen time a day, as long as all homework and chores are done. On a weekend she is allowed longer, depending on what we are doing as a family. You can get apps that police screen time.
Please ignore those who are dead against it. Gaming is brilliant for children.