Help!!!!

so heres the story, i have replaced the thermostat, water pump, heater core, and radiator cap on a 96 VW Jetta GLS 4 cyl 2.0 L and still having problems with over heating. The car idles great no problems with the motor (so it seems) but continues to get well up over the 200 F while just idling for about 15-20 minutes. I read that this might be caused by a cracked head gasket but i was wondering if anyone else had any suggestions for what this might be. Although i am handy with cars this freaking car is driving me up a wall.

My Jetta is a 1990, so may be very different - but 200°f is about what I would expect the normal water temperature to be once the engine is up to full temperature. But the electric cooling fan should come on before it overheats; that is, before it starts to push coolant out of the 'reservoir'. Does the fan come on? On most cars the radiator cooling fan is supposed to also work when the a.c. compressor is running. I dont know if your Jetta is that way, or if it is so cold that it wont work, but if it was working it would be a way to check if the radiator fan is all right. Typically the a.c. system will be turned on when the heater is set to the defrost position - no matter how cold the weather.
If the radiator fan is not coming on, look for a relay that controls it, and check it for loose contacts, or swap it with a new one.
A bad head gasket can result in the cooling system losing coolant. This happens because the combustion gases are blown into the cooling system. Even though the system may not be really hot - the gases being blown into the cooling system are at much higher pressure than the radiator cap (or reservoir cap) can withstand. So it might be pushing coolant out of the system, and not be actually overheated; at least not until enough coolant had been pushed out of the system for the water level to be low enough that the water pump doesnt pump it through the radiator anymore.
If its a bad head gasket, a compression check will likely indicate low compression in at least one cylinder, and it is likely you would see a scummy coating on the surface of the coolant in the reservoir, once you have shut it down and let it cool enough to take the cap off and look in.
If pull the dispstick and see a coating on the end that is not just oil, but looks like chocolate pudding - thats a sure sign of a headgasket that is bad.