Depends on the game. The entire genre of strategy games could probably benefit from smarter AI. More so for 4X style games. Mostly, the current AIs act like players, but make terribly inefficient decisions that get 'balanced' at various difficulty levels by throwing more resources at them or other advantages. So the games vary between being absurdly easy, to being difficult simply because the AI cheats, and even then, it doesn't usually leverage its advantage well. As an alternative, people play against other players, but with long-running strategy games, this adds real life logistical problems. An AI that plays like a human, and can be adjusted for stronger or weaker play would be amazing for the 4X genre. Perhaps difficulty adjustments could even be reverse to giving the player 'cheats' or free resources on lower difficulties if that's easier than throttling the AI.

Outside of those games, I'd say any game with competitive multiplayer could benefit from smart human-like AI. Some people play games for a challenge. The unpredictability of other humans is most of the fun, whereas playing against a typical game AI is just a matter of figuring out how it works, where it fails, and then taking advantage of that failure repeatedly. Considering the market for competitive online games, there's likely a similar market for competitive AI games.

I suspect the real barrier that is that it's a lot cheaper and easier to sick players on one another than to make a challenging human-like AI.