Until a year or two ago there was a stalemate as far as "rich web" development technologies goes. Neither flash, Silverlight or HTML5 was the clear winner. I remember people being incredulous that the iPad didn't support Flash, saying that while it might be ok for the iPhone to not support it, nobody would take the iPad seriously if it didn't support Flash.
In a way, I think it might be the combined weight of the iPhone and iPad that's broken the stalemate in HTML5's favour. Apple sold so many of them, that website makers had to take notice.
When Microsoft announced that Windows 8 metro mode (which may well be the only mode available for low power Win8 tablets) would not support Silverlight, I think the game was well and truly up.
Two years ago, flash was the only game in town; Good HTML5 implementations were no where to be found, and Silverlight adoption was a joke. It's not like you could HTML5 an equivalent to flash on an iPhone OS 3.
I agree that things started changing rapidly two years ago, with the introduction of iOS 4. But there was never a stalemate -- Flash was king; then there was chaos; and now HTML5 is winning (for the time being, though not for long, Flash is still among the royalty). Silverlight had always been a wannabe.
I guess I mean that for people who were considering which platform to build their rich internet app on, there was not a obvious choice.
EDIT:
I admit, there was a time when Flash was the only option, but as early as 2003 I recall "Ajax" being used in preference to Flash for web user interfaces that needed an element of richness. So, I think there has been dissatisfaction with Flash for longer than you imply.
Your choice of words was unfortunate, then - "stalemate" implies a tie with no possible move for any player.
In 2003, there was Ajax rich (you could do some nontrivial client side processing -- like hide and show elements), and there was Flash rich (antialiased polygons, sound). I was talking about the latter, and so do most people that consider HTML5 a worthy flash replacement (even though e.g. you still have to use Flash for proper sound support).
Canvas tag was in safari (both desktop and mobile) and Firefox. Flash (at it's core) is just a canvas you can draw on.
2 Years ago, Flash (or Flex) was immature (for RIA), had poor tools, and poor runtime support (i.e half implemented exception handling, memory leaks etc), impossible to test.
HTML by comparison had a lot of tools for interaction models, and was only immature around canvas (animation/effects). Was easy to test etc.
They were kind of the inverse of each other. Flash was definitely not king. The company I worked at, was working on one of the largest flash apps around, and we constantly had problems with flash, to the point where a silverlight or HTML5 port was considered. (Not sure what they ended up doing).
HTML5 support still sucks. I work with companies daily who are forced to use old versions of IE. So, we're forced to use plain HTML to build our business on, technology is going backwards.
HTML5 support doesn't suck. Check out http://caniuse.com, and you'll notice that non-IE browsers are doing a rockin' job supporting HTML5. If you develop for iOS or Android, HTML5/CSS3 has been a joy. Sure, there are hiccups, but support is far from "sucking".
It sounds like your companies upgrade policies suck! OR, their decision to support/build around proprietary web technologies, hindering their ability TO upgrade. That sucks.
I am/was a Silverlight fan. When Microsoft made it clear that they were focusing on JavaScript (I realize it's not standard's compliant) with Windows 8, I finally spent a lot of time considering the situation. Apparently a lot of the Silverlight team quit or was moved to other divisions. The wriitng was on the wall.
For the last three years, I'd find anyway to build a RIA in anything but JS/HTML. I'd use GWT/Cappuccino/Silverlight/Flex, etc. After Microsoft's move, I finally just embraced JS/CoffeeScript; I love every bit of it.
> nobody would take the iPad seriously if it didn't support Flash
That sounds like revisionist history to me. Plenty of people complained about the lack of Flash and speculated that Apple might eventually have to give in and allow it, but I don't think any significant number of people suggested or believed that the iPad wouldn't be taken seriously without it.
In a way, I think it might be the combined weight of the iPhone and iPad that's broken the stalemate in HTML5's favour. Apple sold so many of them, that website makers had to take notice.
When Microsoft announced that Windows 8 metro mode (which may well be the only mode available for low power Win8 tablets) would not support Silverlight, I think the game was well and truly up.