>>535287941
>is 21 even that popular of a character?
She's the most popular game OC, and a lot of the fans recognize her. While she's not gonna be compared to the franchise's juggernauts (Goku, Vegeta, Gohan, Piccolo, Bulma, Videl, 18) she's in a good enough position. I think possible rights issues with arcsys are holding her back.

>she was never in Heroes which typically has everybody
She was. She was also in one Heroes intro briefly, and World Mission has an extra chapter in its arcade mode where you fight her clones and probably her, and the main story mode has one of the other characters deal with her in a side chapter and Majin 21 is an NPC boss in that (But not a card you can obtain, even though human 21 is).

It was odd she was never part of the main story mode (Either World Mission or the arcade) though...

>then again so would Omega shenron yet he didn't get in either they've really been ignoring him lately in favor of Baby when it comes to GT representation
Omega was "popular" more so because he's the most powerful, final villain. Baby was always more liked as a character. Checking game appearances, they typically share game appearances, but you're right, Baby got some more favoritism in the last years.