I agree AOI is a great film, but it's not one of my top 5 favorites.
Perhaps I took the question as "best" rather than "favorite". I'm a movie buff above all else, and Age of Innocence stands as the most technically impressive and compelling drama she's ever took part in in my estimation. Noni may never work with that combined level of talent again.
I suppose "favorite" would mean something slightly different. Great Balls Of Fire is certainly a favorite of mine. She was adorable in that film.
Side note, do you know where I can find my avatar in high res. I've lost it and it's one of my favorites of her.