Do those other phones you looked at have an airspace under the glass, as most touch devices do? One of the technical achievements with the iPhone 4 and 4S was having the gapless glass layer. Thats why the retina display seems more like youre touching the image, and not touching somewhere vaguely above the image like most touchscreens. A nice subtle improvement.
If the other phone models you've look at are not gapless, then the iPhone 4/4S's Gorilla Glass is bound to look different. (Plus the layer right under the glassthe retina display itselfis bound to have a different surface look even when turned off.) Not to mention, surface coatings are not the same on all phones.
What other Gorilla Glass phone models are you referring to, that look different?