There is no doubt but that .com is trump.  It is the most popular extension on the Internet, and it is firmly established in the public mindset as associated with all things Internet.  Even your newer browsers automatically search for the .com version of a name first.

However, .net is gaining fast, and .org is also familiar, though it is still the most closely associated with its original intended use:  for a non-profit organization.  .Org is also increasingly becoming an extension of choice for people registering their own names or family names.

However, our advice to you is to pick a name and extension that you are comfortable with.  All of them work well.  Ultimately, your success on the web will depend most on your well designed site and its relevant content.