Honestly, Far Cry 2 would have been very good with a few tweaks. First, if:ShotgunSmoke said:ARMA 2.
THE most realistic shooter I've ever played. Also it's boring as hell. Running 10 minutes through a forest, getting to a small village, recieving a bullet from an enemy who's a mile away, then waiting 5 minutes until medic arrives and listening to those HORRIBLE VOICES is not for me.
Far Cry 2 deserves a mention too, but the realism was ruined by guards, who respawn as soon as the checkpoint is out of your view, brand new guns, which jam after a couple of gunfights, buddies, who appear out of nowhere just in time to save you, weapon convoys, which drive in circles and continue driving the same route after being attacked, gun storages, which work like vending machines, the fact that you recieve a phone call right after you've done a mission (how the hell can the caller know what I just did?) and the fact that your character doesn't speak a single word during the game and still manages to make friends.
Rainbow Six Vegas was also pretty realistic and actually fun. Take note, ARMA.
* Weapon convoys moved from point to point resupplying along the way.
* Guards at cleared Checkpoints don't respawn, more soldiers are sent from nearby bases.
* If faction progression actually changed the disposition with that faction. (IE as you progress along one faction's story missions, they become friendly, you gain the ability to call in their forces to secure checkpoints, ect.
* Location based damage. No mobile styrets.
* Some kind of STALKER Clear Sky style faction warfare would have gone a long way towards making the setting feel like a civil war, rather than just a bunch of guys waiting at checkpoints for YOU to come along.
* The weapon system in FC2 was f---ed across the board. I like how the weapons deteriorate visually, and wouldn't even care if that happened as fast as it does if it was exclusively aesthetic. But, that a brand new H&K G3 goes from mint condition to exploding in your hand in less than 24 hours is just plain rediculous. There's no weapon mod system, so, no scoping your G3 or slapping a silencer on the AK47. No high capacity handguns (SIG 226s, H&K USPs, Glocks, ect). Generally I wouldn't harp on this, (weapon upgrade schemes have been over used in games lately), except the additional ammo and durability upgrades seem kind of odd when there's nothing else.
Sorry, I'm ranting, I'll stop now.