If you liked FC3 then go for it.
I personally don’t like FC3 at all, no reason to get FC4. Ubi games are usually boring. Like whole assassins creed series, first ones were new and interesting, later on things change but it’s following the same pattern over and over. Far Cry 2, 3 and 4… Same quests and all. But still if you liked 3, then make sure to get 4.