For people who like rating algorithms, here is the table for top players in the world. AlphaGo is at #4. Also, they don't know if it's a he or a she.
http://www.goratings.org/
You cannot attach much confidence to this rating, because the program hasn't played a lot of games. I heard rumors the top rated player, Ke Jie, issued a challenge to play AlphaGo and Google & Deepmind are interested in organizing a match.
We'll see how that plays out.
In the meantime, you can point people to this site and tell them that AlphaGo might now be the best player in the world, or it might only (ha-ha) be the fourth best! :)
We can now return to your regular Quake programming on this channel.