Most of the approaches used are re-usable, which is a big part of why we can develop new AIs for games faster than ever. You can take the algorithm(s) that was used in one game and use it in another.

Yes, a human is still needed to decide which approach to use, but we are slowly approaching a world where building an AI becomes easier and faster. It will become absolutely irrelevant that a single AI can not play all games, because whenever a new game comes out, someone will be able to build a superhuman AI on it within a week/month.

The brains of an AI are also transferrable. Built a superhuman AI? Send it to a friend! Compare it to a human, who would need to spend enormous amounts of time to transfer their game-brain to someone else. If you want, you can bundle all those AIs into one and pretend it can play any game.

"It's amazing that most people here don't understand that human performance in all computer games relative to AIs is largely irrelevant"