I've noticed this since the release of the game: casual players and noobs think Kirby is the best character in the game by a lot. Why? Because just about everybody I know that isn't on the competitive scene thinks this. One friend of mine even bans Kirby when he plays because he is "too overpowered". The obvious answer to this is that Kirby has the easiest learning curve in the game, and is easy to pick up. The others are that he has spammable smash attacks, a rapid jab combo, and the suck up ability, which is useful when you don't know how to mash out. But seriously, what is up?
Kirby doesn't even have an easy learning curve, it's just that at low level play his stuff seems really good.
Remember, low level play rolls a lot, doesn't tech, doesn't space well, and doesn't shield. They tend to block with attacks, and tend to use B-buttons and C-stick more than the A button because most low level players either can't tell individual A button attacks apart (jab, ftilt, huh? Just mash A), or don't entirely understand the concepts of neutral aerials and tilts.
So most casual players mash the A button, but use the B-button deliberately.
Kirby has an fsmash and dash attack with range (meaning, Kirby fsmash covers rolls and missed techs even if you are poorly spaced). So Kirby constantly can land hits and kills by running and flicking the C-stick.
Kirby has an invincible down-B (remember, casuals use B button moves deliberately), that beats any attacks (remember, other casuals don't shield, they try to block with attacks). So jumping over people and using down-B beats other casual players very hard.
Opposing casuals don't space well, so they aren't able to hit Kirby out of his up-B (which requires good spacing/timing). With five jumps and an up-B, Kirby seems impossible to stop from recovering.
And finally, other casuals don't know they can break out of grabs by mashing, so Kirbycides are guaranteed.
This is why casuals think Kirby is impossibly good.
But why Kirby? I never hear Ike mentioned!
At really low levels of play, people don't realize Ike is good because they have trouble recovering without all of Kirby's jumps, and rely on his B-button moves (which are horrible).
Ike dominates low level competitive play once people realize they can spam his jab and nair. Not casual play, where people usually don't know how to nair.