In my opinion I'd sign up for Epic Games and ensure you get the weekly free games. It's coming up to Xmas so they are likely to have a huge game free at some point based on the past free games (past free games have been GTA5, Batman entire series, Borderlands entire series, Darksiders, Hitman, Just Cause 4, etc - basically my entire library there is free games) also pick up Rocket League for free whilst you're there as that's great fun. Next weeks free game is Wargame. Every Thursday it's a new game free (around 4.30PM our time).
That will start you on some games you'll likely not have played before. If you want to you can sign up for Xbox Game Pass - there are numerous posts on how to get a 3 year subscription for not much money) and this will give you access to Gears of War, HALO, games such as Day of the Tentacle, Full Throttle, Grim Fandago have just been added. They've done a deal with EA to get there games on there later this month as well.
That should give you thousands of hours of gameplay.
M.