Execute the following command
launchctl unload -w /System/Library/LaunchAgents/com.apple.gamed.plist
Verify
grep com.apple.gamed -A 4 /var/db/launchd.db/com.apple.launchd.peruser.$UID/overrides.plist
<key>com.apple.gamed</key>
<dict>
<key>Disabled</key>
<true/>
</dict>