The best Just Cause game, simply because it has the best story, world, and gameplay loop. It's a game that feels extremely focused, with all of the systems in place working smoothly with each other. Visually vibrant, much better looking than the first two games, and also has more likeable characters, including improvements to Rico himself. And traversing around the map with the wingsuit just feels awesome. It's not a masterpiece or anything, but a huge improvement for the series, and just a great time overall.