The worst is Ibara Pink Sweets playing that was a chore. It was so brutally difficult it's not fun at all. Not like other cave Shmups that get it right like Do Don Pachi Resurrection and ESPgaluda. The key is knowing where your hitbox is.
It's a tough call, a Good shmup needs good graphics, balanced challenge and an amazing OST.
Darius always provided that.
But I'm torn I LOVE Cave but Darius, Star Soldier, Parodius all great and how amazing was Battle Garegga?