Is Apple just an anomaly? Also, Sun was bought partially so that Oracle could offer a complete software/hardware package, so I'm not sure your point stands. The others had great runs with great hardware/software... they just didn't survive to the next generation.
And you can add Google and Microsoft to that list, too.
Apple, Google, and Microsoft don't build all their own hardware -- not in the same sense as Sun, SGI, and Cray. Apple uses Intel and ARM chips (even the A4 is a Cortex A8 with a PowerVR SGX). Apple is builds the best cases for their hardware, but the hardware is all pretty standard.