Idk about everyone else, but I think these games are totally underrated. Ok, maybe not totally. But in my mind, they're as good as any classic Mario game, and any Mega Man game. My fav being Kirby's Adventure, cuz that was before they branched him out into these gimmicky side-games like Avalanche and Pinball.
All of them are incredible, tho. The actual platforming ones. Kirby Superstar is an absolute work of art, the graphics are incredible, the gameplay is exciting and weird. They really stand out as unique platformers, and altho the difficulty isn't thru the roof like Mega Man, they're meant to just be experienced, without leaving ur thumbs with blisters.
I kno its a pretty well-known Nintendo franchise, but I still think they live in the shadow of some of these other titles.
And by the way, Kirby's Adventure wasn't the easiest to beat, anyway. It wasn't the heated battle that most NES games are, but towards the end I did feel pretty challenged. It's a forgiving game, but it's still an NES game. Personally I think it's just as good as Mega Man 2 and SMB 3.