She’s had a more constant presence in the games (pretty much is the 4th playable character in games like Shuffle, the Advance games, one of the first 4 unlocked in Secret Rings, already unlocked in the Riders games and part the story mode of first two instead of Shadow ) and non-Sonic media ( has a statue in PSO and PSU with Sonic and Tails, added to Puyo Puyo Quest with Sonic, Tails and Knuckles in the first event, appears in Dragon Coins with Sonic, Tails and Knuckles, playable in Virtua Striker with S, T, K and Eggy ) and has also made more consistent appearances since Unleashed than Shadow has. Lost World straight up just has Sonic, Tails, Knuckles and Amy in it.
And I’m only bringing this up because among the “main 4” Tails is more popular than Amy.
It’s more like a main 6. Sonic, Tails, Knuckles, Amy, Eggman, Shadow.