Graphic novel versions of Shakespeare include the "Classical Comics" versions,

http://www.classicalcomics.com

which may be what an earlier poster had in mind. They produce "American English, Original Text", "British English, Original Text", "Plain Text", and "Quick Text" versions -- all using the same illustrations. So a kid could start with "Quick Text" and move up through "Plain Text" to eventually "Original Text".

Bruce Coville, with various illustrators, has done a couple of nice Shakespeare adaptations, such as:

WIlliam Shakespeare's A Midsummer Night's Dream
ISBN-10: 0142501689
ISBN-13: 978-0142501689

Coville has also done versions of Twelfth Night, Hamlet, The Tempest, Macbeth, Romeo & Juliet.

Tales From Shakespeare, Charles Lamb & Mary Lamb & Joelle Jolivet
ISBN-10: 0810994534
ISBN-13: 978-0810994539
is nice prose adaptations, but not as illustrated, so skews a little older.

Tales from Shakespeare, Marcia Williams
More Tales from Shakespeare, Marcia Williams
-- I think I've only seen one of these in person, but if it's what I recall, it worked well for kids. Each play only got a page? a few pages? But they were very "busy"
pages.

The "Shakespeare Can Be Fun" books by Lois Burdett are written by a teacher who has her elementary students perform these versions. The books incorporate the kids' own art. So whether the style appeals or not may be a matter of taste -- but if you have a kid interested from a performance point of view, they may appeal.
For instance:
A Midsummer Night's Dream for Kids (Shakespeare Can be Fun!), Lois Burdett
ISBN-10: 1552091244
ISBN-13: 978-1552091241