Hellfire, Thunderforce games, Gaiaries, Gynoug, Darius, Gigawing, Raiden etc.
Oh hell yeah, that's an outstanding selection!
The music in many of those 16-bit titles is so good.
PS2 recommendation time!
Gradius V and R-Type Final are absolute must haves if you enjoy that horizontal old-school style. They both have incredible audio-visual style.
Pal region PS2 has decent selection, You might want to consider some of the Psikyo games:
Dragon Blaze
Strikers 1945 (pt1 & 2)
Gunbird (1 & 2)
Senoku Ace (Sengoku Blade might have been released too, Ace is vert and Blade is hori)
Then there are some oddities:
Homura
Gigawing Generations
Psyvariar (actually, I'm not sure this exists in Pal)
And the Cave bullet hell (kinda pricey, but people eat these games up and often never look back).
ESPGaluda (Japanese only)
Mushihimesama (Japanese only)
Dodonpachi Dai-Ou-Jou (Japanese only)
Ibara (Japanese only)
I'm sure I'm missing a few, but that should give you an idea of what to search for.