:) Well, that's good to hear - no one else's opinion should ever over shadow your personal enjoyment of any particular game.
I am glad you enjoy those other games, and I am happy you consider them "great". They don't have music? I consider them not worth playing, but I guess that just shows we have different tastes and values in games (or at least shmups).
Zybex, Scramble, Bulldog, Parallax, Gladiators, Sanixion, Subterenia, Zaxxon, Delta, Slayer, Uridium, Zynaps, Armalyte - I do not class a SINGLE ONE of these as a good shmup. ;) Again, I am happy you enjoy them, but I am thinking I probably don't like them for the same reasons you DO like them.
I class games like Katakis, Salamander, R-Type, St Dragon, Zetawing, Soul Force, Hades Nebula (remix version), Enforcer etc as great C64 shmups. (I purchased Zetawing and Soul Force as soon as they were released ;) )
A lot of those games don't even have sound effects at all, but they all have pumping soundtracks. The sfx in R-Type sound perfectly fine to me, not great, but not crap.... but the music is wonderful, so who cares about the sound effects? Well, erm.... you obviously do, which is odd, but hey, everyone is different.
All of this shmup talk has got me itching for a good C64 shmup..... with a good soundtrack of course. ;)