Ok I do 3d modelling and rendering for a living.
Basically you can't measure the success of a 3D model on it's own because in most cases it's used in conjunction with other materials, brochures, people talking about it that sort of thing.
You also have issues with the way it's rendered, you can have photorealistic versus 'sketch' style and some reports have shown that architecture gets better feedback from less realistic imagery than the photorealistic images. Your idea of a purely photorealistic image may actually give less success because it's the wrong finish for the intended task.
The idea of accuracy (from gord) is fine except when you take into account some initial ideas which are presented to your client don't have measurements to relate to as it's just to show a concept or an idea and so it's scale etc are purely perceptual. You also have characters/models which are distorted deliberately.
Now from a business perspective a successful 3D model is one the client is happy with and is within the current quote and allotted timeframe, and ideally comes back for more lol. If it was for my own scale of success I'd never be happy as I there will always be little things I would like to do differently if I had more time.
