Originally Posted by jeffmd
Yea, crysis is using a fairly advanced vegitation system that LODs trees and plants to multiple degrees of detail, and it is also using some fairly advanced shaders and textures on everything. Alot of its LOD magic dosnt work as much on buildings, atleast not demonstrated yet. GTA4's engine centers much less on vegitation and more on building and streets details. Buildings have a ton of textures that can be toggled and many geometry details that can be faded in and out to gain performance. It also uses a pretty heafty shadow rendering system so that even distanced objects get shadows (although it does start to dissapear when you fly/gain high Z axis).
you are missing one very important factor, CPU. GTA4 is CPU limited, Crysis is GPU limited.