Note that most of recent work in reinforcement learning focus on creating a model which works on all or most of Atari games without using any game-specific know

Note that most of recent work in reinforcement learning focus on creating a model which works on all or most of Atari games without using any game-specific knowledge. If researchers were to focus on only Ms. Pac Man, and ignore the "no game-specific tuning" rule, then Ms. Pac Man, and most Atari games would be solved to near perfection. The challenge that the Atari suite provides is not their individual difficulty, but the difficulty imposed by their diversity, i.e. finding a general algorithm which works well on all Atari games is hard.