I think French is quiet difficult for foreigner imo. Most of the people I know who's picked french in school dropped it after 2 -3 years. I think there's too much exceptions in the language especially with "le, la, les" which could stand for "the" as in "the window = La fenêtre, the book = le livre"...etc.
I think you should choose Spanish, it's much easier than French but the accents have always been a pain in the ass for me. Don't know about Italian but German appears to be the closest to English.
I've also taken Japanese last year but the teacher was awful and i couldn't bear her stories anymore (I've learnt socks' history, wtf?) so i stopped after a year. But Japanese is pretty easy imo, you just have to learn the alphabet (it takes max. 1 month to catch Hiraganas and Katakanas), some vocabulary and particles. Then the phrases' structures which is to me, the hardest part if you don't understand some words. Numbers are also hard to learn at first, since there are different ways of pronounciation whether you talk about the day, the month, the year, the time, your age...etc. But if you're really interested in Japanese culture, then it can't be too hard. I've personnally never been keen on mangas and animes unlike my mates who are almost fluent now.