Hmmm. Favourite theme music...
I'd have to say TNG. Actually, I prefer the TMP movie theme as it's more operatic but there ya go...
DS9 is very good, inspiring but doesn't capture the "Trek" feel quite as well as TNG. In terms of sheer quality though it is as good if not better.
VOY theme is OK but I prefer the "remix" done for the Elite Force computer game (now the series theme of my campaign set aboard an Intrepid-Class ship)
TOS. To quote the great Homer. J. Simpson "Strap yourselves in and FEEL THE CHEESE!!!". But great to listen to when drunk (as I am right now in case you hadn't guessed... ).
ENT song is alright but unfortunately about the only thing that is regarding the entire show.
"That might have been the biggest mistake of my life..."
"It is unlikely. I predict there is scope for even greater mistakes in the future given your obvious talent for them."
Vila and Orac, Blake's Seven