Most online games only work if the person you are wanting to play against has the same system that you have, console, PC or smartphone. There are, however, a growing library of games that offer what is often called cross-play. This lets you play with people on different systems.
These games are a good way to extend the list of friends and family that you can play with. It also makes it less critical which system you have in your home, even if your friends have a different one.
This list includes 93 games from the last 23 years, with 3,432 likes. They come from a range of different genres and play-styles and are all good games if you want to play with people on different systems.