I don't think SteamOS is the best Linux for gaming now, because it is a pain in the ass to get to a bootable media. I know this guy has his opinion and all, but it seems like he doesn't quite know what he's talking about at times. I mean no offence when I say this, but gamers aren't known to be all tech savvy.
There is also the question of the customizable branch, if Arch Linux really deserves the throne. Gentoo Linux is as much customizable, if not more.
Best desktop distro is debatable. I don't think it belongs to any one distro. I think it's very narrow minded to give one branch to one distro, when there are many distros who is just as good as the other, just a different approach.