What are you basing this on? At minimum Chrome and Firefox have better html5 support, as they have near parity with their desktop counterparts. I don't have the numbers but I'd guess Opera Mobile has better html5 compatibility as well.
I'm talking about the browser shipping with the system, which is what 99% of the people using the device are going to use and where web apps are going to live or die.
Once Android starts shipping with Chrome stock things will be different.
I really doubt it has significantly better html5 support than the Android browser, if it's even better at all. But goal posts moving aside, your point was that Safari is somehow evidence that html is important to Apple, when viewed in the context of the entire industry it's above average. Lots of companies are doing good things with html in mobile, even Rim.
Mobile Safari is head & shoulders better than the stock Android browser, which is really a piece of shit. This is abundantly documented all over the web. Just ask the Sencha guys how much fun they've had trying to get acceptable performance out of Android.
Judging the companies by the browser they put in front of users, Apple cares more about HTML5 than anybody else. Like I said, if Google can get mobile Chrome out there I'll revise my assessment.
