I did one year of German, three years of French at high school and I've done one year of Japanese and one semester of Indonesian. Out of those languages I would have to say I found Indonesian the easiest language. Since it uses the alphabet and grammar in the beginning levels at least was the easiest and spelling is phonetic.
However, I recommend that you learn the language that interests you the most or the culture that appeals to you the most. From my experience I found language learning to be quite difficult without any interest in the culture/language. I did Japanese and Indonesian at the same time and I had zero interest in Indonesian culture and alot of interest in Japanese culture, and even though Indonesian was easier in 'theory' I found Japanese alot easier to study for.
Also if language is compulsory, I am assuming that you most probably have to do it for more that one year. If this is the case, no matter how 'easy' the language will be in the beginning it will become tougher as years go by. So, with just the motivation of 'I chose it because it's easy' will proably be not enough motivation later on.
But people work differently and can study something for sake of studying something. Still learning a language at university can be difficult because they teach at a faster rate than high school. Also, if you fall behind it's very hard to get on top of things again. So I feel that you need some kind of motivation to study a language. Anyhow something else for you to consider
, hope it helps you! Good luck