OXM - It can be tempting to lump all first-person shooters together, such is the genre's ubiquity. Battlefield? I think you mean "Call of Duty with more scope wobble, dear". Call of Duty? Why, that's basically DOOM plus sprint and the ability to go prone. Halo? Medal of Honor for Babylon 5 fans, innit. Skim the surface of each specimen, and you'll miss the many intricacies that distinguish them. But get properly to grips with one, and those intricacies will make themselves felt via dismal leaderboard placings and a general team-mate unwillingness to have anything to do with you.