Disabling gamed like this returns no output (unless an error occurs):
$ launchctl unload -w /System/Library/LaunchAgents/com.apple.gamed.plist
$
i.e. It stopped without no error
Should you do the same thing again, it cannot be unloaded as the service is no longer running:
$ launchctl unload -w /System/Library/LaunchAgents/com.apple.gamed.plist
$ /System/Library/LaunchAgents/com.apple.gamed.plist: Could not find specified service
... you've probably already shut it down, or someone has.
Loading the gamed service just executes without response too:
$ launchctl load -w /System/Library/LaunchAgents/com.apple.gamed.plist
$
And similarly, doing it twice tells us we're insanely expecting a different result from the same action:
$ launchctl load -w /System/Library/LaunchAgents/com.apple.gamed.plist
$ /System/Library/LaunchAgents/com.apple.gamed.plist: service already loaded
Continues to works for me in El Capitan. But given that each version of OS-X and iOS are getting more and more polluted by mandatory services that actively connect without the knowledge of the user, and that iOS-specific commands/errors are in the man pages everywhere, someone is approving the dogs to be off leash on the permanent 'connectification' of every users' bits and dots. Why not make a big thing of 'disabling game functions'- let alone build services that work just as well configured with or without cloud and social connectivity? Supporting users to use the market differentiating aspects of OSX seems more sensible than forcefully 'productising' users and user data. /rant