Someone has to be the party-pooper...
Much of what passes for graphic design stinks.
With the advent of the personal computer, untrained civilians started taking matters into their own hands and away from the professionals, jauntily desktop publishing, font fondling and templatizing their "so called" designs into aesthetically-challenged brochures, websites, logos, mailers, sell sheets, etc.
Why settle for Leroy Neiman when you can have the Mona Lisa?
There is indeed a difference.
Exceptional graphic design means your marketing communications will be more unique, targeted, and better looking.
You'll get a logical messaging hierarchy, images and typography in balance, strategy translated into graphic design solutions, project objectives met, white space where it should be, a sophisticated color palette, controlled chaos if required, compelling concepts, print production knowledge, and technology serving the design, not the other way around. I could go on, but will stop now, hoping I've made my point.
Hire professional graphic designers, educated at the best schools and with experience working in the trenches with the best firms. Your product, service, business, and/or company may require this level of expertise to achieve and maintain a competitive edge.

"Design is so simple, that's why it is so complicated."
~ Paul Rand
Graphic design examples by Clemans & Partners.