Well Flash is a tradmarked and patented software etc by Macromedia, now Adobe. html/css/xml etc are general languages now really owned by anyone. There are a few alternitives to make flash files without using Flash itself, like Swish, but nothing is as powerfull.
Most people hate Flash because they only see sites that use it poorly and/or have bad impressions from the late 90's. Just how people still think macs are so expensive and suck, mostly due to bad impressions early on.
But Flash is what I do, I've been doing it for 6 years and it's wonderful. Anybody who says Flash is easy, probably either has had much experience before using it, or isn't very good at it IMO. Sure it may be easy to make a few animations, but to master it and to be able to make QUALITY stuff isn't easy at first. It has a high learning cure. Sure, once you understand it it's easy, like everything else you learn.
A lot of the bad things people say about flash aren't Flash's problems: they're the designers/developers fault. Really, you can make a accessible fast loading site in Flash as easy as you can make a slow loading horid page in html. It's all dependent on the developer.
Check out
The FWA: Favourite Website Awards - Web awards at the cutting edge it's the leading award site for Flash. You can't tell me that any of those sites suck, or they were easy to make.
Now it's also up to the developer to know the right and wrong times to use what tech. Sometimes it's better to use Flash for something, html for others. All of that comes with experience.