You just suck. Use Boomerang Cutter, foo' - he's amazingly easy.
And I've always found the originals to be more difficult. Some of those Wiley castles were obscene; especially that one where you start with two weapon energy capsules, yet you're better off not taking them, trying to fight the boss once, losing, then taking them when you come back. Course, I did find them easier then I recalled when playing them on the AC.
The Wily castles are the only challenging part of the originals.
And I don't have the Boomerang Cutter. I'm going by recommended order, which is Chill Penguin, Flame Mammoth, Storm Eagle, and then Sting Chameleon.