The post using NES as a comparison is the main problem, in my opinion, especially given that Quake in 13k of javascript exists (only 3 levels, but still), which is a closer apples to apples comparison.

Besides, "needs to run on a multitude of browsers" is not hard unless you decide to make your javascript do absolutely everything, and even then it's easy to keep it working on the major browsers, you just aim for the lowest common denominator (usually Safari). The browsers do the heavy lifting of running on a multitude of OSs and architectures.