I know this is stupib, but what game should I play for my PS3? Skyrim, MGS5, Minecraft, or BO2?

Skyrim. The other ones are games that get boring quickly, but Skyrim is a timeless game in my opinion.

Yes, "Skyrim" it with its three add-ons (aka: DLC, Down Load Content; "Dawnguard", "Hearthfire", and "Dragonborn") have thousands of hours of repeated game play. (I have over 3500 now, in my 14 th go through).
Even the basic game (just "Skyrim") you should have enough to keep busy for 100 to 250 hours of play.

The Game never truly ends. There's no Credit Roll. You can stop playing at many points to start over.
With Hundreds of minor missions to do for the NPCs, some of which are level or deed controlled might not be noticed. You have Random Deaths that can prevent the availability of them.
With a number of Either/Or decisions you must play the game at the very least Twice to get to do all of the missions.

BO2 servers are kind of dying down by now. I don't know about MGS5 haven't played yet, but the other two you can sink hundreds of hours into. I prefer Skyrim over Minecraft though