If you have had the oil changed on a regular basis, chances are it isn't a lifter. A bad lifter will make a ticking noise not a flapping noise.
As far as the wheel bearing, if you hear the noise when the car is stopped, it can't be a wheel bearing. A bad wheel bearing will make like a howling noise that changes with speed and intensity when you make turns. Does that happen?
As far as the serp belt, try this little trick. Start the engine and open the hood. Pour a small amount of water on the belt and see if the sound changes. If it does, then the belt could be an issue. Do that and let me know what you find. Just FYI: the only time I have heard a serp belt make a flapping noise was when it was tearing apart and a piece of it was flapping around.
Sunday, September 8th, 2013 AT 6:25 PM