GITS wasn't even a 'mega hit', as far as I am aware, it just did quite well.
That's actually really hard to prove in the West anyway as nobody releases jackshit in regards to overall sales number(or atleast as far as I'm aware).
I'd ask you to further explain what you mean by "relatively huge". TV ratings? Disc sales? Visibility and popularity inside the anime fan community? Visibility and popularity outside the anime fan community?
Nielsen ratings for the first season seemed to be decent although it quickly fell in the second season. I also don't have access to disc sales anywhere.
Edit: Sorry was in a hurry. Anyway I would just say visibility inside and outside the anime community. Granted it's very anecdoctal.