In my humble opinion, MS Outlook 2010 should have provided a default way of viewing ONLY Unread Mails. It is a lot easier to change the view of your folders and take a look at only Unread mails. Here is how you can do it [in case you aren't aware]…

    Click on View -> Change View -> Manage Views…

    Click on New… button

    Name it Unread and ensure Table is selected. Also ensure All Mails and Post folders is selected. Click Ok.

    Click Filter on the dialog box…

    Go to More Choices and check Only Items that are: Unread

    Click Ok thrice… and you will be back to the main Outlook Window.
    Now, you will get one more option for Unread mails in your Views.

    This should work on all of your folders.

I hope this helps!

Until next time,
Rahul