The hardest thing is to read every post before you reply

No, I can't do that, just read the first third or less.. or the last.
I haven't met with many westerners who learned any eastern asian languages... Though I can believe it's hard for them. To Hungarians, however, I think Japanese is much easier - the word order is different in Hungarian than other European languages and the writing system is phonetic. (And actually we write our names family name - given name style, like japanese/chinese). Chinese would be more difficult for the intonations already mentioned. At least I find it difficult to reproduce a word I hear (Ok, Singapore is quite a mix of languages). Anyway, it seems to me that Hungarians (at the rare moments they are motivated), can learn most languages easily, probably easier than english-speakers. But it's not statistical sample...
Btw there only about 55 or so hiragana and katakana, surely not a big number. And only about 2000 official kanji. In China I don't know, but think they use way more kanji. And there you have the traditional (used in Taiwan and in calligraphies) and the simplified writing (used in mainland China); and in seals (for names) they use a very old type of writing (something from 1..2000 years ago, i'm not sure). The calligraphers and literature ppl know all three...
Many (or most) of the Japanese (and also Chinese) people I met had problems with English. One reason for this can be the different sounds (like there's no distinct r and l there, not English also tend to not pronounce r

). Another reason might be the education system. Reading the blogs of some expat US teachers, they mentioned they were not allowed to teach using their own methods, but the japanese have their own ones, which, as seen, are not efficient (someone from Japan, enlighten me pls if it's true...). I had a similar feeling with Russian people. I've seen them reading English text from paper - it was written down phonetically in cyrillic (btw it's a funny activity, to try and guess at a conference etc whether they do this or not). When my father was learning in Russia looong ago, they taught him such pronunciation as 'zis' for "this" and 'ze' or 'zö' for "the"...
For me presently the hardest language is Singlish. That is, Singaporeans speaking local dialect of English (something like pijin-english). Even if you learn the chinese (all dialects) and malay words in it, the pronunciation (esp of chinese mother-tongued ppl) can be terrible for me (having had american teachers (not from texas,though)). Sometimes I can't recognize they are actually speaking English... And the funniest is when two guys talking, one in Mandarin, and the other in English, and understand each other. (younger generation Chinese here often speak English as mother-tongue, and they usually speak the British one).