Several RPGs have good replay value. The ones I remember most are Alpha Protocol, Mass Effect 2 and The Witcher.
Other than that PC games have free mods that increase replay value. Most mods are released for Unreal 3 and Half Life 2. Counter Strike started as one of these as did Team Fortress.
Other than that PC games have free mods that increase replay value. Most mods are released for Unreal 3 and Half Life 2. Counter Strike started as one of these as did Team Fortress.