Which languages take the longest to learn?

I've had a fairly random exposure to languages and can read German, Dutch, French, Spanish and Portuguese a little. I've also watched a huge amount of anime so my Japanese knowledge leans towards "leave it to me, i will transform and beat up the bad guys". I've worked on numerous text processing projects for Asian languages so I know certain things about the characters but could only read the easy ones like 一 and 人.

In the last few years I've gotten increasing interested in Chinese traditional and pop culture and I lately I got involved in a project involving the creation a "second brain" of a sorts that got me looking first at content with English metadata, then content with half-Chinese, half-English metadata, and I know there is plenty of Chinese-only content waiting for me.

I had the experience of starting to have proper nouns start to stick out "that has to be somebody's name" and then I discover that the I can look up the syllables in the Unihan dictionary and it is the same as when they write that person's name in English. Then I go to the library and get some books on Chinese grammar and that's what I read on the bus these days -- I'm having more fun with the grammar book than I've ever had learning a language, I do try to pronounce phrases because a friend told me "you learn a language with your vocal cords" but I haven't gotten references for the pronunciation and I really suck at pronunciation so I am not trying to get the tones right yet.

I'm experimenting with scripts that show the pronunciations and meanings from the dictionary side by the side with the text and that really does help with the "characters you don't know" problem. It's really amazing the extent to which the semantics of the characters compose to build words.

(ranging from 600 [dutch] to 2200 [chinese] classroom instructional hours)