Gun Showdown on PSP came out 4 years before RDR1, and it also nails the cowboy vibe, with such a small open world and janky controls. : r/reddeadredemption
PSP Gun Showdown for Sale in Stanton, CA - OfferUp
Gun Showdown multiplayer details | GamesRadar+
Gun Showdown Game for Android - Download | Cafe Bazaar