I’d just be honest and say you see him as a friend now - I don’t have anything against people playing games, but it seems like he prefers investing his time in those and not in you. That’s not a reflection of your personal worth, either.
And “we grew apart” is often a cover for poor behaviour on the part of the person who uses that excuse, sorry to say. At the very best, it’s an indication that they didn’t want to put the effort in to try and fix their relationship with that person before calling it a day.
Good luck with whatever choice you make, here. I know it’s usually tough breaking up with partners, but it is better in the long run!