We don't have many fans for FC3 and FC4 apparently. I enjoyed both very much, FC4 in particular. Among other things, the use of music and environment design were especially quite well done.
Never played the first Far Cry. On the other hand, I remember the second one fondly, although it really suffered from all the valid points made so far (recurrent spawning of hostiles at outposts, fucking malaria, constantly jamming guns, terrible vehicle control, broken stealth mechanics etc.).