WHBM,
I was contrasting CGN with CVT. Granted, Hahn has no such facilities, and granted, there is a cost element attached to this infrastructure, but I think it is fair to say that Germany has the best integrated airports when it comes to making links between flights and onward rail journeys.
FRA, DUS and now CGN are served by ICE stations, whereas STR, MUC, HAJ, HAM, THF and SXF have direct local or urban rail / metro links. If I've missed any out, please correct me. SXF will also have an ICE link when BBI is opened, although it will be interesting to see if the locos are offered the option of using the old terminal (another thread?).