Why magento for ecommerce?

1.
FREE: You do have to pay for support.
2.
Multi-site functionality: Creating additional websites on one unique domain.
3.
Ability to import huge spreadsheets of product.
4.
Searching and sorting of product by several criteria.
5.
SEO functionality is built-in, tags, descriptions, very clean urls, site navigation and clean html.
6.
Integrated Google analytics.
7.
Built in functionality for all the major merchant accounts.
8.
Newsletter.
9.
No limits on number of product or purchases .
10.
Integrated sales and store tracking.
11.
Google base formatting & support for downloadable products.

All of the above points mentioned by "Fadi Alkhateeb" are true.
Just to add up some ....
1.
Plug And Play.
Many extensions are freely available which can be integrated very easily with magento connect manager.
2.
Reliability.
Recently I integrated almost 35000 products in my store www.saletab.com and it worked amazingly stable.
The system never crashed even if you will load a huge data feed.
But on the other side I would like you to review the negative side as well.
1.
Expensive hosting.
Magento dedicated hosting is very expensive.
2.
Magento architecture is not easy to understand as compared to other frameworks.
3.
Magento developers are very expensive.
4.
Magento is difficult to customize.
By customization I mean molding it according to your needs.
I will prefer magento as super best if you can afford the following.....
1.
Expensive resources.
2.
Expensive hosting.
3.
You have less customization requirements.
Then there is no question about magento.
Go for it.....

Really good to work with magento. since it offers loads of great extensions with helpful features. looked at different stages, its an adaptable one and better approach to fabricate the ecommerce stores.

Refer: https://www.apptha.com/blog/magento-trounces-virtuemart-shopify-oscommerce-and-others-in-ecommerce-race-survey-2013/

Magento ecommerce solution has become the most demanding open source platform of today's online retail store businesses since it provides a tremendous advantage.
With Magento Ecommerce Platform, online store owners are being given the capability of handling multiple stores and facilitate a more systematized browsing of items for sale.
Improved management of customer’s orders and having more developed promotional or advertising tools also comes possible with Magento Ecommerce.
Andy iLoveMage.com

All of the above answer is right the most and main feture of magento is you can manage many store through one admin.