The new beta version of Flash 10 comes with hardware acceleration for 3D. This could prove to be the real advantage point Flash needs over technologies such as Silverlight.
As a C# developer and eager games developer, I’d love to see this in Silverlight. I’ve always wondered why one have been relying on software rendering in RIA technologies such as Flash and Silverlight when the graphics adapter is perfectly capable of doing this a lot better than the CPU. Let the CPU do what its good at and the graphics adapter likewise. For cross-platform compatibility one could use OpenGL as a platform for this. I guess doing that would be quite the camel to swallow for Microsoft, an abstraction of some sort would enable them to take advantage of DirectX on the Windows platform and OpenGL on Mac and Linux or any other platform. The only issue would be devices such as a Windows Mobile or a Nokia mobile telephone that wouldn’t be as powerful in 3D rendering. But I think that problem should be left to the content developer to choose how advanced graphics they want in their content.