Wonderboy 3/Monster Lair is long, and brutal. I'd say it's a runner-up for the "Duomazov Measure of a Turbo Bad-Ass" game list.
I have only beaten it once, and I was significantly buzzed/drunk at the time. True story. Not so intoxicated that my reflexes were severely impaired (obviously), just enough that I was a little "looser" than normal and just enough that my memory of the event is a bit foggy.
I've been unable to duplicate the event in a sober state.