I know this game gets a lot of hate, but I consider it one of the best far cry games in this series. Not as good as 3, but better than 5. I've been waiting for another island based game since I finished far cry 3, and this one absolutely does not disappoint.
What I didn't like was the after story. The Insurgencies make absolutely no sense, given that the Castillo government ended with his death. Where are the special forces coming from? They're just seems to be absolutely no thought put into it, other than how to keep people playing and wandering around repeating the missions they've already done. Only the excellent game mechanics keep me going back to it, not the stories.
The co-op was terrible as well.
But if you're a single player kind of guy like I am, I really don't think it gets a whole lot better than this.