I'm not big on bullet hell shooters, so that'd probably make me an outcast in most shmup communities these days. Even though it's no shining example of the genre, I'd even take Otomedius over the average bullet hell if only because it plays more like classic shooters. I actually like having stage design to interact with, so when you got a bullet hell shooter with completely empty screens save for the enemies and bullets, I find it boring. They seem to revel in their cheapness too, while I prefer shooters that are challenging but not being intentionally unfair.
Anyway, the TwinBee games were the first shmups I really got addicted to. It's still my favorite shmup series. Pop'n TwinBee on Super Famicom is probably my favorite, but I love the PC Engine version of Detana! TwinBee as well, even more than the arcade original since the port is more balanced. My favorite shmup period is probably Dragon Spirit, but I'm actually not that big on the arcade or TG-16 versions. Even though it's a downgrade in graphics, the NES version is faster and tighter. As you can tell, I really like shmups with two planes of combat, shooting enemies in the sky and bombing enemies on land. As for horizontal shmups, I'd probably have to go with Gate of Thunder as my fave.