The MaLDoHD mod that adds more HD textures to Crysis 2 that makes it look like this 

vs the origonal (note not the same area)

With over 1000 new textures ways in at just 808MB

@zarx: That spectacular improvement in Crysis 2 in due only thanks to the texture pack or does the DX 11 patch has also something to do with it?

@zarx : I am not sure what's your point, there was no suggestion that this is not possible to implement it in such way, only that in the way Square-Enix implemented it does(for whatever reason, development cost, quality, some kind of performance boost avoiding compressing/decompressing, install time, I dont know whatever).

Also texture? crysis use textures as well, what size is the new HD ones, 4K ?

Well the DX11 pack is required, it also has some extream DOF which is pretty horrible, but more imortantly it has parallax mapping (givs the illusion of depth to the cracks) and specular map (gives the shiny highlights) added.

pack uses 2k by 2k mostly vs the base mostly 512 by 512, and all games use textures. As for Square Enix using more space I get the impression that the guy was talking about the unoptomised CGI quality assets that were used in th demo vs what would be actually in a game, and he interpreted the question as if they were going to use that quality of assets for an entire game but that is my interpritation. It could be they don't reuse textures or at least reuse less, RAGE for example uses Megatextures where every single inch of the enviroment has it's own unique texture which pushed the game up to 22GB, but that is kinda wasteful in terms of development resources for arguable gains.

Ok, so it's thanks to both the DX 11 and the textures.

Thanks.