well i can't talk for "people" but i can talk for myself and i really liked the original
to be fair the actual game is really simple,you just punch monsters until you are strong enough to take care of the boss,if you are aiming for a high score you will go for the kill as soon as possible (which might be too soon) if not probably until the game says "OK! you are strong enough! go kill the boss!"
what makes it shine is that the game is divided in 50 scenario's and each scenario is different,full of secrets and wacky,in one of the scenario the boss is a black and white monster called CATS who seems like he just got out of a old gameboy game,his power consist of turning the land into black & white and he quote zero wing intro (he declares "ALL YOUR COLOR ARE BELONG TO US") if you reach a certain place before he GBize it and put a secret code,you get a secret weapon
in another scenario you have to defeat a really strong boss and you can go north or south,if you go south you make a pact with a demon and you go into path A,if you go north you team up with a cleric which puts you into path B,if you defeat the monster without the help of anybody by grinding yourself silly,you get a secret achievement
in another scenario the big baddie has removed all of the monsters on the map (so you can't grind!) so you ask for the help of an hermit and he decide to train you,normaly you are supposed to just train until you are strong enough to defeat the boss and complete the map but if you grind yourself silly,the hermit issue you a challenge,if you beat the hermit (and he's REALLY strong!) you gets extra equipment!
(NOTE: consider that "grinding yourself silly" in this game means wasting 5 minute on a map instead of 2)