Here happens to be my favorite out of Pokemon Conquest. I find myself coming back to this song many times
http://www.youtube.com/watch?v=rwyur5tzbBs

Also, favorite song from Gen V
http://www.youtube.com/watch?v=xc_0wfIuuzw

Gen IV? I spent hours in this route just to hear it loop
http://www.youtube.com/watch?v=Uir_5l6zeZw

Gen III
http://www.youtube.com/watch?v=ZOoqKHz_D0w

Gen II
http://www.youtube.com/watch?v=1q6AXyI2oPY

Gen I, it may be spooky, but also has a calming sensation.
http://www.youtube.com/watch?v=u8NktOkmRvM