9. Switch Between Batman & Catwoman - Batman: Arkham City
Batman: Arkham City introduced New Game Plus to the Arkham franchise, which removed attack indicators while also changing enemy placement, making them stronger and faster, and also kitting them out with more powerful weaponry.
The legendarily challenging trial-and-error boss fight against Mr. Freeze on a second play-through was reason enough to keep playing once you'd rolled credits on the main story.
But it gets even better.
The player is only able to fully complete Catwoman's DLC mini-campaign once the main Batman story is finished, after which players are granted the ability to switch between Bats and Cats as they wish.
With Arkham City's sprawling open world freely available to players for the post-game, you can mop up any remaining side content and police the streets to your heart's content while constantly swapping between the two iconic superheroes.
What more could you possibly want?