You know, I can't for the life of me understand why anyone still harps on about returning to Sonic Adventure style... WHY?
Because for me its the best Sonic game ever made and I think you're missing the point of Big the cat, when comparing it to the Werehog sections. To play as BIG the cat was 'entirely optional' and there lies the key difference between the Werehog sections which were not optional at all.
With Sonic Adv you just played as Sonic, it was up to you if you wanted to play as the other characters to add to the games length and that's what I want in a Sonic game and that's just to play as Sonic !. It's what killed the likes HALO V for me, I didn't want to play as anyone else other than the Master chief, or MGS 2 when I only wanted to play as Snake.
Looking over that Sonic Adv was a fantasic adv , I loved the hub sections , the speed of the game, the set-pieces and the level desgined captured every great about Sonic game with its cool attitude and action, never mind the game having one of the best music scores in video game history and if that wasn't even it even had a pretty good pinball game in it too.
That game was a true labour of Love and also Windy Valley and Speed Highway are my fav Sonic levels out of any game