"It's hard to resist the temptation to just outright cheat and save all the time" - Say, that's what *I* did!!!! For the really hard ones anyway.
Your Super Metroid comment reminds me of the fact that I bought a crappy SNES-imitation Gravis joypad to play those emulator games with...and then just gave up and used the keyboard instead.
The password system was shared between Metroid and Kid Icarus, both released simultaneously in 1986, with Metroid said to be by far the better seller of the two (KI as a character was only used for a Game Boy spinoff that was basically a remake of the original KI--no glorious Super NES sequel like Metroid got). It's pretty long winded (four columns) as far as passwords go; the most famous Metroid password is "JUSTIN BAILEY ------ ------") so that you can play as Samus in a one piece leotard (a "bailey," I guess--"just in bailey") and in Kid Icarus it's "8uuuuu uuuuuu uuuuuu uuuuuu" to get to the last level with all the weapons and stuff, and another one is something like "DANGER TERROR HORROR !!!!!!!" but I forget what it does.