Re: I thought that HTML5
Anyone serious about porting a large game as a webapplication uses WebGL.
For example, you take your existing OpenGL C++ game engine and 'just' recompile it with Emscripten/LLVM to 'asm.js' and run that in the browser:
https://www.youtube.com/watch?v=BV32Cs_CMqo
(Mozilla and the game engine developers did that port in only 4 days !)
But people have been using it for other things as well, how about porting emulators of old computers to asm.js/Javascript. For example to play old games:
https://archive.org/stream/The_Hobbit_v1.0_1982_Melbourne_House/The_Hobbit_v1.0_1982_Melbourne_House.z80?module=spectrum
They ported MESS which emulates a large number of devices:
https://archive.org/details/consolelivingroom
Or a DOS-emulator, so you can play 2400 old DOS games, like:
https://archive.org/details/msdos_Wolfenstein_3D_1992
If DOS works, you can make WIndows 3.1 work too, so they did, with Internet access:
http://ascii.textfiles.com/archives/4546