With a few exceptions, no, it is not.  If you have at least 3000 reputation, you should vote to close.  We want the community to be involved in moderating the site.  See https://meta.superuser.com/questions/3154/how-should-my-flagging-change-when-i-gain-the-ability-to-vote-to-close

From http://superuser.com/privileges/close-questions:

> Note that once you gain the reputation to vote to close, you should no longer flag for moderator attention to have questions closed or migrated. It is your responsibility to vote now.