Bread isn't bad for dogs, they just don't have a digestive track long enough to digest most of it. That's why most dry dog foods really aren't that great for dogs. Yah they survive just fine on it, but why do you think the majority of dogs in the US are obese?
Its just like with people. We're eating more processed, high-grain content foods, and exercising less, and the result is obesity.
Truthfully, the best diet for your little pooch is a completely raw diet, composed of chicken, beef, turkey, and some oily fish like sardines. Plus carrots, green beans and broccoli mixed in (but ground up very fine-again, the short digestive track makes it difficult to digest unless its pre-ground).
The raw meat needs to include a high percentage of organ meat and bones, as these are an essential part of a dogs diet. The best foods for dogs (easiest to acquire as well as good for them) are turkey/chicken necks, wings, thighs, legs, and organs (hearts, gizzards, livers, etc.). Then add in some ground chuck or "stew meat" for some variety, add in some fish occasionally for the oils, carrots regularly (whole, as this really helps clean their teeth) and green beans and broccoli occasionally.
We just switched our dogs over to a completely raw diet about 2 weeks ago. We've already noticed a difference. They are much more interested in food, they eat better, they are going to the bathroom less often (because they are digesting more of the food they are eating), their stools are smaller, don't smell as bad, and decompose faster, and their coats are getting shinier. They've started to slim down to a healthier size. Oh, and they aren't nearly as interested in "kitty crunchies" as they used to be.
This diet may not be for everyone, because you do have to handle raw meat on a daily basis, and some people just aren't going to do that. Plus you have to sit and watch/listen while your dog crunches through chicken wings and turkey necks, which isn't necessarily the most pleasant sound. BUT, your dog is likely to be much healthier in the long run.
At least, that's my opinion.