If it were to be ranked the right way Kingdom Hearts wouldn't be on the list at #21 I doubt it. If they are talking about from 2000-2010 or even just last ten years from 2002-present. I still couldn't see it ranked that high. Good game no doubt, but man are there way more.
Mentioning GTA's, Halo, COD(depends which one), God war, FF(again depends), and etc. Basically it would have a while before it showed it's face.
But as with everything it's one's own opinion so I digress.
I noticed something. Kingdom Hearts I ranked #21 in the list, but also Kingdom Hearts II ranked #43 in the list! When I read the description they did of Kingdom Hearts II, I really was like "WTF!!", I couldn't believe what I was reading. I will copy it below:
"Continuing right after Kingdom Hearts, Roxas, Sora's nobody, travels across the Disney worlds in order to merge with his true self. Drive gauges help Sora and Roxas gain new forms in combat and traveling in the Gummy Ship is a game in itself."
I couldn't stop laughing when I finished reading the description! Hahahahaha EPIC FAIL!
Certainly, this ranking isn't done by people who know a lot about the Kingdom Hearts series. They even put in Kingdom Hearts I an image of Kingdom Hearts II... Aside from this, I find the list very objective.