The right place to start off exploring what makes good graphic design - would be to first restate what we mean by graphic design.

 So here goes with a defination as written by Jacci Howard Bear -

"Graphic design is the process and art of combining text and graphics and communicating an effective message in the design of logos, graphics, brochures, newsletters, posters, signs, and any other type of visual communication. "

As you can see - the definition pretty much encompasses the graphic design services put down in the last post.

The key issue to take from the definition would be "communicating an effective message" - the be all and end all of any design project.

Graphic Design is not simply an art form, created for aesthetic pleasure or simply for people to stare at and wonder whether their 3 year old could do any better and also make millions by having a drawing of a pink square on a blue background hung up in the Tate - it is not just about any type of communication.

No successful business owner  would commision a new brand identity simply to look pretty or impress the neighbours (note the keyword "successful"). Rather, the brand would be created in order to effectively communicate the service/ product/ added value being provided.

In other words, the message must be received at the other end.

So most definately - the first rule of Good Graphic Design - it has to communicate an effective message.