The best dry dog food is the one that works for your dog. It might have corn in it, it might not. It might be grainfree (in which case it probably has potatoes or peas or tapioca as filler instead) or it might not. Dog food is full of advertising ploys that can make you go crazy.
Learn to read labels, understand ingredients and make your own choice. What works for someone else's dog is not necessarily good for your dog. If your dog is doing fine on his current food then I would pay attention to that old saying, "If It Ain't Broke Don't Fix It." A lot of dog food changes can set your pup up for intolerance issues.
I like the site I linked below for how to read labels and understand the laws governing them and what ingredients really are. Not the ratings section at this site, which is out of date. And on that note, also be wary of sites that rate foods, they are often out of date and just one person's sometimes uneducated opinion. There's just no shortcut to learning about dog food, it's best if you educate yourself.