Generally .. Russian language is attractive because of its inusual alphabet ... it's awesome ... :)

Well because it's a different language and has a different alphabet to most other languages and it's simply an awesome language :) Simple .

may boys finds Russian girls so pretty and for marring them they are learning Russian :)))

The Cyrillic alphabet is similar to the Roman alphabet, so it is easy to learn unlike say Arabic or Chinese. Maybe there is a bit of the красивые девушки factor. Also I feel that much of the world still sees Russia as a superpower, so it is a respected country. To me it has a nice sound too. Russians are nice, sociable people and can be found all over the world. Russia also sits between Europe and Asia and has had long links with both.

You could ask in addition: "Why do so many want to learn Russian and why do so few do it actually?".