I think you could make the case for multiple online games to have the ability to improve a few skills.

Mainly games where you are teamed with random players (especially MOBAs) and must communicate and use teamwork. Games like Scrabble might improve your vocabulary.

Communication is just as much a skill as any and useful in the real world. That's not to say that it's going to help if nobody has the mechanical skills or if your characters/items are inferior but dealing with defeat could help strengthen your coping skills or you can go back and analyze it and find more efficient plays (analytical skills).

Not saying that even a small fraction of people do any of this. Most people probably play games (especially mobile) for just a little break in the monotony of life and put them down when they are done.

I like to believe that Starcraft has improved my ability to multitask. Also, resource management. I'm able to apply delayed gratification to my army by building stronger units that cost more later by investing more heavily in economy/upgrades/technology early on based on the state of my opponent.

Also, Ultima Online has a bunch of player-run servers. Someone came out with a client that injects packets to the Ultima Online servers, so I was able to learn to write "fault tolerant" programs. It was a huge motivator for me to learn to be a better programmer.