I'm Spaniard, so yeah, I'm also a little annoyed for not seeing Spanish in the poll. I've seen your reasons for not putting it, tkioz, and... well... it just doesn't cut it.
Spanish is the second most spread language in the world, second only to English. In rough number, more people speaks Chinese, but that's because of China's insanely huge population. Even with that, Spanish would be in third position.
If you knew about that, there's no way in hell you would have skipped it. That's just plain ignorance. I don't mean to be offensive, but I can't use a softer word. For this situation, it just doesn't exist.
In any case, English is definitely the language with more options for the international language. It already is to some degree. In this globalized world, you need it as second language, minimum.
And it is easy to learn. I've studied French, German and Japanese, and English is objectively easier than all of them. Hell, it's probably the easiest language in the First World. Even though phonetics and spelling can be a pain, the grammar is way simpler, and you can make yourself understood with more ease than in other languages.
In Spanish phonetics and spelling don't put any problem at all, since every letter has a single sound which is virtually unchanged regardless of how the word is written. But grammar is way too complex and deep. Specially verbs can be REALLY tough. Even when I was at school there were students who had a hard time learning all the conjugations. And I'm talking about native speakers.
In any case, every single language on Earth has its unique beauty. You can like some language better than others, but every single one of them has characteristics you won't find in any other. And every language can give beautiful texts if you use it right.
So I think that everyone should at least try to learn two languages minimum. One of them English for pragmatic reasons, and of course, master his/her own native language.
And for native English speakers... don't be lazy and try to learn a second language already. lol