Flash was blazing trails doing widespread use of RIAs & XML data exchanges long before AJAX took off (or the term AJAX was even invented). RIA (Rich Internet Application), by the way, was a term coined by Macromedia with regards to how Flash was used. Before Flash started doing what it was doing, surfing the web meant reloading entire HTML pages or the marginally better iFrames (which were a compatibility big headache back then because of the browser wars between IE & Netscape) to make simple data calls.
Flash has driven the ubiquitous and acceptable use of internet video, saving content creators from the huge costly headache of having to support multiple formats. Not only that, but Flash has made video interactive, allowing everyone to embed videos as entire rich mini-websites even non-tech savvy end-users can stick on any webpage they wanted.
Flash is the reason why casual games and the web games are so popular now, especially with both genders. Now, Flash is going to have full GPU hardware 3D acceleration, gamepad support and will be running on upcoming TV set top boxes including Google TV: http://tv.adobe.com/show/max-2010-keynotes
HTML5? Every single HTML5 demo you see now is playing copycat catchup to what Flash was already doing 5 years ago.
Think about it.
Can't wait to see what the web will be like in the next 10 years.
(btw, big shoutout to http://opera.com which has been responsible for most of the innovations modern browsers have today such as tabbed browsing, tab session saving, thumbnail preview buttons to your favorite sites upon opening new tabs, and speed, speed, speed http://bit.ly/aeEuFO )