It sounds like the crucial trust element is still there, however you feel that yourself and himself are gradually growing apart. It is important you nip this in the bud as you see it becoming more of an issue.
You need to talk to him and let him know that this is bothering you, confront him and point out that it's rare for the two of you to do things together lately and that you want him to help you understand why he spends so much time gaming. Don't throw your hands up in the air and give up talking to him- it's the worst thing you could do.
He's starting to neglect your relationship; nothing wrong with gaming but too much of any one activity isn't productive. Good luck.