Which DBMS do you think is best to be used for storage? Oracle, MS SQL, PostgreSql, MySql And do you think there might be a reason to avoid any?

Oracle is the best for data storage.

If your application is based on lot of data then you should avoid MySQL, PostgreSQL. Like if you are developing application where the whole nation's people records are going to be stored.

as you arranged the DBMS names like Oracle ,MS SQL ........as of my knowledge Oracle and Ms SQL are the best. 

Oracle’s new database cloud innovations support more businesses than ever leverage industry-leading enterprise capabilities while simplifying access for IT Users and developers.

Newest data management capabilities enable all sizes companies of to safely and easily migrate workloads to the cloud.

Oracle has massive cloud scalability. It has rapid analytics which works faster time to insights.

@umair I knew there is a hard competition between Oracle and MS SQL and I thought PostgreSQL is an advanced DB engine as they claim. Governments and large scale businesses tend to use Oracle; I thought this is for stability sake but it turns out you are correct. There is a whole bunch of engines and only a few are reliable.

http://db-engines.com/en/ranking

Thanks for answering