Understand how the RPS mechanics work and then play the game and figure stuff out. Grab beats block, block "beats" attacks, attack beats grab, etc..
After you have a grasp on that and how use it to land attacks, then pick a character, watch/read a beginner guide for that character, and try to have fun and learn while you're getting your ass kicked online.
You might also check out "Gief's Gym." I've heard it's a good resource for new players.
Castlevania was not even good at the time of its debut. Ghosts n' Goblins could run laps around it despite being released a year earlier...
Are you kidding me? I played through both Castlevania on the NES and Ghouls n' Ghosts on the Genesis for the first time a couple years ago when I was on a retro console kick. Castlevania instantly became one of my favorite 8-bit games, and even motivated me to play through Simon's Quest(bleh) and CV3. Ghouls n Ghosts was fun for sure, but nowhere near as clever with its difficulty or level design.