I think the classification game is stupid, but of course it's interesting from a standpoint of understanding the marketing opportunities (or pitfalls).
The PC-Engine came out in the last quarter of '87, in Japan. There it was doing very well as a game system with ultimate graphics that rivaled many arcade games of the time.
Both video processors (a Video Color Encoder and a Video Display Controller) were 16-bit. Just like the SNES, the system's main strength was its custom video hardware, but its failing seems to have been the main CPU's speed.
One thing of note is that both systems have a processor descended from the 6502 (of the Nintendo Entertainment System/Famicom), the Western Design Center 65C02 of the PC-Engine/TG-16, while the SNES has a custom (slightly improved) version of the WDC 65c816. The PC-Engine's chip ran at over 7 MHz, while the SNES's CPU can theoretically run up to 3.58 MHz, but in practice the CPU is pretty much restricted to running at 2.68 or even 1.79 MHz. Regardless, Wikipedia's Apple //gs page contends that the chip which eventually became the SNES chip was faster than the one that would become the PC-Engine's. It's not certain how system bus constraints end up hurting the SNES processor in comparison to the PC-Engine's, however.