I liked both Far Cry games, although I agree they're way different.
Far Cry was awesome because the tech was so new. Look! I can see more than 50 feet! Look! There's a shadow on my gun! A SHADOW! On my GUN!! Don't get me wrong - it's a great game, but that was some of its appeal.
Far Cry 2 is beautiful to look at and does a very convincing job of making you feel like you're in a different part of the world (unless you actually live in Africa, I suppose). The gameplay is fun, too, and the self-healing animations (like pulling a bullet out with pliers) are neat and add a lot to the feeling of being there.
Where 2 falls down is the insane respawns. You can kill everyone at a checkpoint (which is ANY place that two dirt roads cross, all of which are heavily defended with machine guns, grenade launchers, etc) and then drive down the road a ways, turn around and come back - and get a fresh crop of bad guys.
It makes it impossible to just roam around the game world unmolested, which is a shame, because it's otherwise clearly designed to be roamed around in. Every mission requires traveling a long way, and lots of side missions can be found along the way. So yeah - kind of an open world that demands you wander around... and then punishes you for it.
I have started and quit 2 or 3 times because of those stupid respawns. Everything else is super good, though.
Oh, and the weapons degrade kinda fast, particularly the dart gun. You fire a dart, and suddenly your gun is all dirty and banged up looking. It's funny. Sorta.