CV64 suffered from the following problems:
-It was rushed, therefore unfinished.
-It sucked to begin with.
-Konami had the balls to release the game again, with the 2 characters that didn't make it (except they basically had minigames instead of being part of the story).
The concept was OK (CV in 3D), but they failed to make it work. However, they COULD make it work if they tried. Their last 3D Castlevania attempt also ended up in the trash, so there's also a chance that CV is cursed when it comes to 3D.
On the plus side (or downside), another GBA CV game is coming out, with another "musical word" of the "dark or nighttime word" title. Forgive me for saying so, but Symphony of the Night Jr's are not really that fun, and you can't see them for shit anyway thanks to Nintendo being filthy homos.