i mean if i am contributing something there i must get back some return apart from satisfaction that i am helping others!

Ideally, that is kind of the point of Wikipedia, so it may not be for you. Blatant promotion, propaganda, and personal benefits have a pretty good chance of getting edited and/or cut pretty quickly.

It is a good place to pick a topic and use that as the basis for honing skills in writing, thought organization, research, source documentation - all of which could serve you well outside of Wikipedia - even if helping others through sheer chance.

It is an evolving project. I am not involved with it, but use it is as a source. Independent verification of facts is important more than ever - and harder to provide due to the volume of data and repeated data in the world that is not valid.

Selecting a single topic and developing to a high standard should pay off in your everyday work.

what are the benefits(any form) of writing articles in wikipedia

The only benefit I can think of is a good "backlink" to your site. Also, in time if your website grows and become famous, you'll have additional visitors via wikipedia.

For me it is a long term investment but as you said, helping other people is a greatest reward of all. :)

I look at Wikipedia much like WebmasterWorld. You can give a lot and learn a lot. I use it as a resource, but jumping in would be like a drug for me. There are some dedicated people doing very good work that should stand up well over time.