iphone safari vs. opera mini, pie, etc

[abdeviation]

I just have a straightforward question. What feature/technology does the iphone safari browser support that make some sites work so much better on it.

I'm talking about the google mobile sites in specific. If you go to gmail.com on the iphone, you get an interface that's almost as usable as the desktop version. not the case on any other mobile browser. Or say you go to maps.google.com, same story. What's safari got that we don't?