Really? It doesn't seem to me like much Intel-written software has been key to x86's success. The things I can remember from Intel are compilers, performance analysis tools, and threading and math libraries. But none of them were must-haves, or differentiated x86 chips from competing CPU architectures. Most of the software that made x86 successful came from third parties.
And more recently, the reviews I read of the Archmage graphics drivers didn't make it sound like Intel had understood the importance of the software that was essential to a pretty big hardware release.