I only have two hands, so I can only play one game at a time.
Now seriously: in general, I have a long term game I often come back to play during a long period of time. Currently, Street Fighter 6. Then there are games I buy most of the times super cheap but don't play, and other games I buy and play during a relatively short period of time. As an example, I got the recent TLOU2R upgrade for 10 bucks, watched the extras and played the new mode to unlock Joel and complete it with him. That took me a few hours. I might play a few hours more to unlock his skins. Once done I go back to SF6.
Then there are games or trials from PS+ or game codes shared by some dev friend to show me their game, which from time to time I only play during in most cases (normally I don't complete them) a handful hours to test it.