If you are looking for other games created by Gameloft as well, don't bother. Most multiplayer games will become dead (no updates/no player-base) once the money from in-app purchases stop flowing in.

I don't even think there's a game similar to Six Guns on the mobile market though; however, I do recommend moving towards PC/Console gaming since there will be more choices to choose from (good examples are Red Dead Redemption & the upcoming sequel, both console exclusive though).