Counter-Strike is described as '(CS) is a series of multiplayer first-person shooter video games, in which teams of terrorists battle to perpetrate an act of terror (bombing, hostage-taking, assassination) and counter-terrorists try to prevent it (bomb defusal, hostage rescue)' and is a very popular first-person shooter in the games category. There are more than 50 games similar to Counter-Strike for a variety of platforms, including Windows, Linux, Mac, Steam and Web-based apps. The best Counter-Strike alternative is Call of Duty. It's not free, so if you're looking for a free alternative, you could try Unreal Tournament or AssaultCube. Other Counter-Strike like games are Valorant, Tom Clancy's Rainbow Six, Splitgate and Garena Free Fire.
Fantastic predecessor to CS, kept alive by the community. The class based combat keeps the game fresh.