Jst how hard is English for a Japenese ?

Is it harder for them to learn English than it is for us to learn Japanese?

english as it is, it's a simple language

(IMHO!) it's easier for Japanese people to learn English, due to a couple of reasons. Romaji is used to write hiragana, katakana and kanji on their computers, which means they are already exposed to the latin script from a young age. (not the case for English speakers, they have to start from scratch to learn katakana, hiragana and kanji)
They are also more exposed to English than an English speaking person is to Japanese, be it through the Internet, a bit of TV, etc.
Most young people will do decent in the written English language, but you'll be hard pressed to find actual proficient SPEAKERS of English language.