I have to say, that in my experience, it has to go in the following order:
General < Videogames < Art < C&C < Audio < Flash < Politics < Wi/Ht? < Programming
General gets filled with thoughtless +1 posts and a lot of spam, and many of the regulars even join in with this, so (despite the fact that some of the members are amongst the most intelligent on the site) the average intelligence is pretty low.
Videogames is, despite being what you'd think should attract the most idiocy, generally made up of intelligent regulars. Many members drag it down a lot, though.
Art is where the BBS starts to get into the intelligent side, but due to the fact that most posts are spacefillers for images it's hard to rate their intelligence.
Clubs and Crews is extremely hard to describe, as it contains some of the most intelligent, and least intelligent, posters on the site. Even the intelligent seeming clubs can often attract unintelligent members, as I have seen, and the unintelligent seeming clubs can attract intelligent users.
I've never really visited Audio, so I'm going to place it beside the other creative forum, the Flash forum.
I started off my time on the BBS as a Flash Forum user. Although I rarely ever visit there anymore, I enjoyed my time there and most of the users there were far more intelligent than your average BBS users, and were very helpful in every situation that they could be, even when faced with the type of questions that they had about six times every single day (literally). These constant posts are what drags the Flash Forum down, but it's still one of the most intelligent forums in my opinion.
Politics contains a large amount of the most intelligent users on the site, but amongst them are a lot of the least intelligent users on the site. I don't visit there frequently, but when I do I often see threads created to convey a purpose, but the user who creates them does not provide any evidence at all, and is little more than a line long. Usually one of the more intelligent users provides some reasons for their point or asks them for some, but there are still a lot of people trying to convey a purpose with a point and nothing else, which takes it down slightly.
Where is/How to? is where a lot of the oldest (in both age and time on Newgrounds), most mature and most intelligent users on the site congregate. The regulars consist of helpful users who are avid B/Pers, posters and have a long no-missed deposits chain, which shows that they spent a lot of time on Newgrounds and are therefore very well accustomed to it. When I look through the Members and Regulars lists you always see intelligent users who obviously put a lot of thought into their posts, despite what it's about. I hang around in the Regs/Members lounge chatroom, and there's always interesting discussion going on there, as well. Maybe I'm ranking it high because it's where I spend most of my time, but I definitely know that there's a lot of intelligence in there.
Programming is probably one of the forums that I lurk the most, but due to the fact that the discussion is usually very technical, I rarely ever write posts in here. I'm pretty good with computing, especially for my age, but the regulars here are extraordinarily intelligent and are on another level of intelligence to most of the users of other forums on the figurative and mathematical side.