I'm not sure what market cap has to do with it? BHP Billiton is an _actual_ commodity (mining) company with a market cap similar to AMD [1]

GPUs aren't commodities in the traditional sense, it's more of a figure of speech to convey how interchangeable and standardized GPUs are nowadays.

[1] https://www.google.com/finance/quote/BHP:NYSE

Consumer game hardware is small potatoes in the revenue stream of those companies. They might be important to the game-playing consumer, but they're regarded as commodities by industry.