PC98: Even between Easy and Normal
EoSD, PCB: Even between Normal and Hard
IN: Hard, sometimes Normal
PoFV: Normal, rarely Easy
MoF: Normal, sometimes Hard
SA: Normal, sometimes Easy
UFO: Even between Easy and Normal
IaMP, SWR, Hisoutensoku: Normal
I'm not very good at these games yet (barely beat the first three Windows games on Normal), so I play mostly for survival and not for score or 1cc. Right now, I'm trying to get over a hatred of ultra-fast projectiles, skewed circular patterns, crazy level enemies, and especially lasers.
I only find Easy mode useful for learning the individual games' mechanics and strategies. For serious play, it's only for tiny baby men running from Sandvich elementary school children those who cannot accept "game over" as an answer.