@alyssa sonic adventure (not 2), sonic advance series (sonic advance 2 makes her downright obnoxious to unlock though; i never did it), sonic heroes… sonic boom: rise of lyric, i guess…

sonic the fighters (if you want a fighting game) was the only game with her playable that retained her old design from from sonic cd, where she was introduced (literally only to be damseled and then fall in love with sonic when rescued). until sonic superstars i think.

most (all?) spin off multiplayer games make her playable