You can take a look at this post: http://www.totalgadha.com/gmat/2009/05/business-school-profiles-average-gmat/

This would give you a rough idea.

I don’t have a really high gpa. It may cross 7 on a 10 point scale. If i get a competitve score in gmat exam will i be eligible to apply to the top B-schools? Kindly advice.

The quality of work experience means career progressions, promotions, displaying of team skills during the project, handling a team of “X” number of peopl effectively, completing special projects successfully etc.

A good work experince should reflect examples/ anecdotes from your real life, your learnings, experiences, how you manage things, how well you implemented you skills, did you get any promotions, did you take any initiatives at work, did you resolve any queries among your peers so on and so forth.

Someone working in a company for 3 years at a same position would have less weightage than someone who has worked for one year but have displayed more growth and skills during his short duration at the company.