Any phone is going to look like new if you put protection on the front, back, and sides...
Indeed, which is why I do it. However, for non-glass-backed phones, you can't keep the original back look in general easily. Glass accepts a clear protector easily and it still looks good. With plastic, metal, and rubberized backs, not so much. The option then is just the full-on case.
BTW, for my Android phone, I don't have a case or bumper because the phone is so damn wide in the first place.
It should be noted though that glass backs without protection do withstand scratching much better. There is a good video at iFixit with a 2 year old kid scratching the hell out of the iPhone 4S vs. the iPhone 5. After the kid-test, the iPhone 4S looks like new, but the iPhone 5S looks like crap. That is a fault more of the iPhone 5's anodization, but the same holds true to some extent for other phones.
But like we said, the drawback is that glass can shatter if dropped.