Suppose I'm writing a 2d tile based MMORPG.
Furthermore suppose I hate flash.
Lastly, suppose I only need my code to run in the latest safari, latest firefox, and latest chrome.
What are the limits to what I can and can't do? (Are there examples of good game engines that only require a recent web browser)?
Thanks!
Check out the Unity3D engine: http://www.unity3d.com
Cross-browser, cross-platform, although your users would have to download the unity browser plugin...
For something that works for the user, OOBE (without add-ins etc); Javascript is probably the only unified functionality that exists between all browsers.
The browser is surprisingly quite capable (at least Chrome is), this is something that Google Chrome is attempting to promote (see http://www.chromeexperiments.com/). Notice some however, that experiments are often laggy or unworkable in other web browsers.
As for a list of things that are and aren't capable; that would take a fair while to compile.
In regards specifically to a 2D tile based game, I wouldn't say it isn't possible, but it may be quite difficult to create. As mentioned before, most browsers (apart from the stand-out; Google Chrome), suffer from limited resources. Therefore resources wise, it may be difficult to implement and would defiantly require a lot of requirement fore planning.
Look into HTML5 Canvas http://en.wikipedia.org/wiki/Canvas_element
The latest versions of the browsers you mention already support it.
It depends a lot on what programming languages and game engines you already know. And what kind of game you want to make. If the game require real time graphics or nice responsiveness. Then you CAN'T use FLASH or Java script or HTML5. You must have a game engine or a fast programming language like C#.
I suggest you take a look at Roozz which allow you to run any game engine inside any browser and they support cross platform and cross browser. They also support advanced copy-right protection and automatic updating of clients. Soon they will also support pay-per-use. Like flash it require users to install a browser plugin.
There's also the Raphaël javascript library...it does a very nice job of abstracting a lot of the heavy lifting you'd have to do otherwise! The memory footprint seems decently light as well (from my small-scale playing around with it anyway).
You could also move to 3D. While it does require a plug-in (although is being integrated into Chrome), the results are undeniable.
"O3D is an open-source web API for creating rich, interactive 3D applications in the browser." http://code.google.com/apis/o3d/. The video is quite amazing actually -- especially the live map editing (e.g. removing sprites).