I think because it came from three languages like latin, french and german, and it's the newest language in the world, and because the most strong country use it, I like to hear new Idea, maybe there are other reasons why English is the most important and polular language in the world ?
Some reasons I thought of quickly.
1) English can be spoken in many different accents and dialects and still be understood. Some other major languages like Arabic and Mandarin have variants that are not understood by all speakers of the language.
2) Great Britain had an empire and colonised lots of places, meaning speakers of English spread to different parts of the world.
3) English was adopted as the predominant language in the USA, which was the superpower of the last century.
4) A lot of popular films, music and TV shows are in English.
As a native speaker I have no experience of this but my friend who learned it as a second language said he thought English was relatively easy to gain an intermediate level in. He was comparing it to German which he had also studied. Not sure whether its true or not, he probably had more incentive to learn English because its more widely spoken in the world.
I think English is easier to learn comparated with other languages as Russian, Japanese, Chinese, French, Spanish, etc.
Interesting question and I think Paul pretty much covered it. I think his reason #4 is an important factor of why many people enjoy learning English. Many of them already enjoy the output of our entertainment industry. Learning English can make our music, movies and TV shows more enjoyable.
I think Paul's second and third points are the main reasons, and they partly explain point four. I don't believe English has special inherent qualities that make it "popular" - we use it due to a long history of speakers being pushy, stubborn, bullying... and holding the cash. Not a pretty picture, but that's how I see it. Money, military, mass communication.
Ивансоткин, what you do mean by English being a "new" language? It's relatively old. It's been around for about 1,500 years, constantly mutating, and was already in a recognisable form (recognisable to modern speakers, I mean) about a thousand years ago.