Well, i hope my POV can help answer your questions.
1. The girls aren't necessarily "perfect" but in most series specializing in fanservice or the ecchi genre, they pretty much have these so called "perfect" figures. Its all pretty much to attract new watchers, usually around the 14 years olds and beyond.
2. There are quite a few black people in some animes that i could name, but you're mostly right. Majority of the characters in anime are of lighter skin color, most likely because Japanese people aren't black? lol
3. The big bubbly eyes have no particular reason. Every artist/manga/animator has their own way of drawing or showing certain facial expressions. Its through these that the viewer can closely relate to how the character(s) is feeling. IE: A certain death or something of the sort.
4. Plot definitely changes VERY fast in most animes BECAUSE they have 12 episodes to give out the meat of the story. Now, this doesn't necessarily apply to the bigger series, like Naruto or Onepiece. But, most new and upcoming animes only have one season to show their stuff. New animes come out on the same channels about every season. (Spring, summer, winter, fall.)
For example, a list of all the Fall animes that were just released a few weeks back.
http://images.google.com/url?source=...gv_152UbcOCG8g
I, for one, still enjoy anime, mostly for a deep plot/storyline (especially those that give off a light-hearted feeling, romance, etc). Its just like watching any other tv show on hulu.com for me. Really, though, rather than watching the anime, i would prefer reading the manga for a less "rushed" experience. All of the details that weren't included in the anime(s) would be in the mangas as well.