Linux

If you follow the history of the Mac, it went through a number of major architecture transitions from 680x0 -> PowerPC -> Intel -> ARM. Each time, Apple supplied a decent emulator to support applications during the transition.

From a developer perspective, these were huge upheavals that came with a lot of drama but also offered some opportunities. The latter came from the fact that the bar was in some way set higher on the new platform and you could count on any code you compiled for it supporting certain base features. Every PowerPC, for example, had hardware floating-point. Before that, some CPUs did, some didn't. The Intel transition happened at the time when dual core had become standard and SIMD had become serviceable (with SSE2). The ARM transition has set the bar at 64-bit architecture for every CPU (since Apple had earlier dumped 32-bit on the iPhone side).

Windows/Intel has developed in a more evolutionary than revolutionary manner, which is easy to see if you look, for example, at all the legacy cruft in the Intel ISA. It's a sad sight. Supporting all that makes instruction decoding a nightmare. In theory, Intel/AMD could reinvent a new sleeker ISA if they could get Microsoft to commit to supplying a performant emulator for the old one? But I'm not holding my breath.