I actually gave up on Far Cry some months ago but came back to it last week after a fresh install and started from the beginning again. The first time I ws playing, I got stuck on 'Regulator' which is level seven.
Playing on normal, I managed to get up to that level again in one evening and wondered what I'd thought was so hard the first time around.
I'm now up to Archive, which is level Twelve (how many levels I got to the end then?).
In my opinion, it is one very classy game, easily on level pegging with HL2 imo, but I also think it's very hard. It's also very frustrating in places as there's no save feature, except the auto save, and you don't know when that's going to happen.
I've played many scenes over and over again because of this, very frustrating.
Good thing about Far Cry is there are many ways to go about many levels, one route may prove very very hard, whilst another may allow you to pick off the enemy one by one before they even see you.
So, getting back to the original subject of the thread, Far Cry is as Stealth as you want it to be (just like reef said). I reckon the more stealth you use, the more chance you have of making it to the next Save point.
Really, really good game though, me is loving it