I think Nostalgia has alot to do with people thinking certain games are better than others. Ocarina Of Time is nostalgic for me, in a weird way it's the game that has made me who am I today. If it wasn't for Ocarina Of Time, I would have never had a website, would have never met any of you, and never found my fondness for working with computers.
I remember when it was storming outside really bad and I was playing the Forest Temple in OoT, and there really isn't anything memorable, I just remember playing that level while it was storming really bad one time.
But I feel like most people won't accept a game of today to take the place of games they have fond memories of. I think in 10 years (as that's how long it's been since OoT came out), that people might be more inclined to believe that GTA 4 is the best game of time, not that I'm saying I think it is however.
Well, to call a game the best game of all time, there's a lot of factors you need to consider. GTA4 may be the most fun game some people have ever played, I'm sure. But OoT is far more qualified to be called the best game ever. Think of the innovations it made. It invented the 3D action adventure, and every single game of its kind released since has taken a lot from it. OoT is a true classic in every sense of the word - it's still as fun to play today as it was then, and I'm sure another 10 years won't change that.
I'm sure GTA4 is great. I haven't played it. But is it really the best game of all time? Really? Think about that one very hard.
In the end there's no single best game of all time, anyway. Everybody has their own favorites. Gameranking's list is dumb anyway, cause both versions of GTA4 and both versions of the Orange Box make up 4/10 of the list.
Best game ever is tough. I'll always be partial towards KOTOR. Morrowind and Oblivion are both good examples. Also games like Ninja Gaiden and RE4, both of those are perfectly executed on the gameplay side, but naturally lacking any kind of deep narrative. Not really that big of a deal, just feels weird to call either of those the greatest game ever made. I think OoT is a pretty good choice, but I about agree with Bayli that Twilight Princess was even better.