Hi.
The problem is most action browser games, whether short arcade style or full on mmorpgs like runescape or puzzle pirates very heavily graphical.
There have been one or two attempts to build arcade style games in flash, but even there screen reader support can be interesting, one reason why the flash version of blind swordsman was better downloaded than played online.
The only browser games I know that are not text based drive, sudosan, and These games from gamevial such as colonel zeeg and rebound.
Actually the gamevial ones are pretty cool as far as they go (I rather enjoy rebound), but obviously they're smaller arcade titles.
The closest thing we've got to something more complex, multiplayer and realtime would be either muds, or the few sound based mmorpgs we have such as survive the wild and before it's demise deathmatch, though manifestly those are client based rather than browser based.
I confess at this stage of development, where everyone has a working internet connection I do wonder what value there might be to creating browser based action audiogames, especially given that the platforms used to create them such as unity and flash have fairly dodgy relationships to screen readers, where as a custom client of course can be %100 screen reader friendly.
I suppose there is the question of cross platform availability,even then you have the screen reader issue, though I suppose there might be some cross platform potential if you could! get flash or unity to create a self voicing game and thus obviate the need for a screen reader, ---- though again good 3d sound support is in either platform I don't know.
Getting back to the question at hand, Drive, sudosan or the above mentioned gamevial games is probably your lot thus far, though on the plus side if you haven't played the gamevial titles I'd recommend giving them a go.
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)