Scarecrow wasn't scary... ever, for me anyway.
Batman on the other hand had several moments of scariness... when he's gassed Crane and has all that black dripping from his face, and then in the Narrows with the red eyes and mouth... SCARY!
The only time Scarecrow is visually kickass is on the horse, and even then it's the horse that's cool looking, he's just along for the ride.