Astro Boy is older.Even then, I still hear that people think that one is apparently garbage and "low-effort".
I know what an icon is, maybe the better word is influential? I seriously doubt Shonen, or Akira Toriyama's art would even be a thing without that character. Goku is totally right up there, but Astro Boy literally turned Japan on it's head back in the day. He's the character that birthed manga, and anime for that matter. I totally get what you're saying with Mickey Mouse and Snow White, but that's really not a fair comparison. I think people who aren't from Japan underestimate how iconic he is because just he's such an old character and because of the fact that he isn't being used much currently.
Thats it.
Watch Dragon Ball and DBZ, you'll literally see Toriyamas influence in everything.