You should try three mods. If you are into realistic, AI(of course) and Better graphics. You should get the following:

Reallife Sis, Cheeky name i know but it makes the lighting and graphics better. Great!

Advanced AI, Does just what the name says, it makes AI better. Now you cant just take out a minigun and blow the suckers out, you have to be tactical.

And then the last mod. Reality Enhanced. Makes everything more realistic. Weapon sway if not crouch, prone or strenght, Weapon deal balanced damage,

and so on.

Here are the links:

Reality Enhanced: http://www.incrysis.com/forums/viewtopic.php?id=15792

Advanced AI: http://www.moddb.com/mods/crysis-advanced-ai

Real Lifesis: http://downloads.guru3d.com/Real-Lifesis-Crysis-Mod-download-2253.html

These are all great mods, they can also be combined to make even greater gameplay! Have fun.