picturemail aka MMS will be reduced in quality due to the restrictions Sprint have in place for sending such files.
OP, are you new to sprint? if not, this reduced quality of picture mail has been the same for quite some time. more than likely what you're seeing is normal.
take a video and then attach it. you don't have to send it just take it, and after the phone converts it to send via SMS, click it and look at the quality.
in the stock SMS app, there are settings you can adjust, but probably they won't make much of a difference.