Hi
EDIT: Forgot to mention that they work very nicely as game music :)
From a musical point of view, just as steve mentioned, there's too little micro dynamic. By that I mean "realistic" use of articulations.
If you don't know how to use key switches for changing patches, you can watch a great video in the user area.
Try doubling some instruments, or add a different score in the backround.
Also, you should check out the velocity cross-fade (f.i assigning it to the mod-wheel). It will allow you cross fade between the different velocity layers, and I feel it's essential for obtaining a realistic sound.
On the production side, you will get a more realistic sound (it's really alpha-omega) by sending each instrument to a reverb channel (or several), and mixing it in the total sound image. It's quite common to set all sends to pre-fader, so you can control the precense of an instrument with the channel fader, and if needed adjust the reverb as well.
Hope this helps:)
Good luck
-Fred