SHow me someone who beat it in even 24 hours back when it came out. Those games were lengthy by sheer newness and hardness. Sure people can speedrun them but that was after spending countless hours dying over and over.
I never beat that game. I could get to Frankenstein's Monster and Igor without losing a life every time, but I don't think I ever got past him. I tried over and over again, but never beat that boss. I think it was a mental block, but I would love to go back and finally beat Castlevania! I love the sequel, and could beat that in 20 minutes or so after a while, but Castlevania 1 was too hard for me. Heck I even beat Mike Tyson's Punch out many times without beating that stupid Frankenstein's Monster in Castlevania.