Intel decided to leave the low-margin microcontroller business a long time ago. ARM may have gobbled up the market, but there's an entire graveyard of companies who were unable to make it in that highly competitive market.
The Cortex-M world is dominated by peripherals, more so than core performance. A faster or more-accurate 12-bit ADC is what makes your company live or die (or STM's "op-amps on board", which reduce the need of external opamps, a singular opamp + cortex-M3 chip is all you need). Integration is key, not so much performance or even power-efficiency.
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In any case, I stand by my primary claim: ARM Cortex-M chips do NOT compete against Intel in any capacity. They're a completely different market. Intel doesn't have the technical expertise needed to make ADCs, Timers, or Op-amps like say, ST-Micro or TI. (Lower-power OpAmps, higher-frequency, lower-input current, lower output impedance, compatibility with a wider variety of voltages from 1V to 5V... etc. etc. ).
