HTML5 will eventually take over as the technology of choice browser based games. Already you can start to see the trend shifting away from the now dominated flash with some developers dabbling with the new HTML5 technology. Over the next few years I expect to see an even larger shift in the number of games produced using HTML5 as the standard becomes more mainstream and browsers start to better support the features.
HTML5 offers developers several advantages over flash and does not require any plugins. On top of all that the fact that HTML5 is a free open standard which has a pretty good track record of beating out proprietary options when it comes to the modern web atmosphere. These options make it an excellent choice for developers to use when developing new games.
Currently casual browse based games are almost all exclusively written in flash. Check out any gaming portal site and you will find that pretty much every single game on their site is flash based. So before the new HTML5 technology can be accepted into mainstream usage for games, HTML5 game portals will need to developed that can replace the flash ones currently being offered. This will give players the ability to browse and find the HTML5 games just as easy as they can find the flash games in the way they are accustomed to.
The future looks bright for HTML5 games as each day more and more HTM5 games are popping up on the radar everyday. One by one developers being attracted to the technology and are starting to create some really great games. Even through HTML5 very new and is estimated not to be fully implemented until sometime in 2020, all major browser already support sufficient features for the creation of full blow games. Check out some of the HTML5 games created here on this site and you can see easily they rival their flash counterparts in quality and play-ability.
HTML5 will soon be the future of online games. It is very true that the web is currently dominated by flash games, but that trend is starting to change. In coming years as browsers begin to support more and more features game developers will start to produce more and more games. Take a look at these HTML5 games. Remember HTML5 is still a very new technology and it will take a while for the to get to the quality (and quantity) of games to equal that of flash games available, however having said that there are already numerous high quality HTML5 games that are both fun and free to play.