Gran Turismo 5 is a good looking game, but we're really starting to compare apples to rocks now ...
It is possible to exploit the limitations in how a game is played in order to maximize the overall appearance of a game; certain genres (like fighting games and racing games) have many more potential exploits than other genres. Even within a genre two games can have very different requirements which enable one game to look better while using fewer resources; and example of this was FEAR, a game with environments more static than early doom clones which enabled them to pre-calculate all of the lighting and drastically improve the overall appearance.
Now, I don't know how dynamic the environments in many of the games being compared to Crysis are but being that Crysis' environments are (pretty much) entirely dynamic and there is (pretty much) nothing that can be exploited to improve the visuals it is a technical marvel.
