I think you know you've got a good game, when I merely booted it up to capture five minutes of footage, and end up playing for six hours. I've heard for years that Just Cause 3 is merely Just Cause 2 with prettier graphics, and I couldn't disagree more. I replayed some of Just Cause 2 as well, and the third game is just so much more refined, polished, and varied visually and in-gameplay that the idea of going back to Just Cause 2 seems pointless.
Don't go in expecting an groundbreaking experience, but go in expecting a free one, and persevere the extremely linear opening. Once you get passed that, it's far too easy to just get lost exploring, taking out bases, and testing every combo of weapons, vehicles, and destructible.