To me, perfect media can and do exist, though rarely. Perfect, of course, meaning that they are as good as they can be without being something else. This means they aren't necessarily the best, but that no element of them could be improved in any way. An example is that I think Tequila Sunrise is a perfect song, but I don't think it's the best song and it isn't my favorite song.
In gaming, there are few perfect games. Most games shoot for the moon and forget to hammer down the most basic things and trip over their own feet loaded down by a topheavy concept. Most perfect games tend towards simplicity. Portal is one a lot of people might point out.
But for a better game, I've always considered Ico to be perfect. There simply isn't any single aspect that could be improved without altering the scope or nature of the game itself. It has a short list of goals, and they are all accomplished as well as they could have been.
This is why Ico, in my opinion, has held up so well over the years and will continue to impress long into the future; the things it accomplishes are not elements of technology or even mechanics, which will always become passe and outdated, but of theme and concept, which the years cannot diminish and the ages cannot improve.