Shadow of the Colossus is in my personal Top 20. Just know that it's not a fast paced blockbuster. You traverse a huge, barren world to slay 16 colosi - it's very meditative and artsy. It's an experience you won't forget, that I guarantee you.
How much time do you have? It sounds like your plate is full but if you have bags of time to sink into an open world RPG try Horizon: Zero Dawn. Massive open world with plenty of side quests and the like, and one hell of a great backstory.