Iko MattOrr
Smash Champion
She's still a classic character, and her influence is still present in recent games, even if she doesn't appear directly. Look at Elline, it's just Adeleine+Ribbon, even the name is similar.I wouldn't compare her to Olimar when he's the original star of one of Nintendo's latest IPs. He represents pikmin . Ado wasn't the main star of K64 nor is K64 the beginning of a new IP. Bowser Jr is the secondary villain of Mario and has appeared as recent as the NSMB games.
Kirby 64 is one of the most memorable Kirby games, maybe it's not considered the best one but it's one of the most important games being the first polygonal Kirby game. When they selected the classic Kirby games to make the 20th anniversary collection, they included Kirby's Dreamland 3 and 64, and Ado/Adeleine was in 2/6 of the games, in one of them she had a major role in the credits of the game, and in the other she was even a main character, on par with Dedede; I think that this alone brings her above many one-shot characters or secondary characters that only do some cameos at times.
Even if she hasn't appeared in a new game, she still appeared in the Dream Collection, that's a recent game: she has a character description in the booklet, and her keychains are in Triple Deluxe even if unnamed (Normal Daroach also is not present, he appears only as his dark version, so I think it's due to a strange selection they made).
Anyway, everyone has their points for supporting their favorite characters I assume.