The Apple ][ was a breakthrough machine, because it came preassembled, had video terminal functionality that worked with a TV, and a full BASIC burned onto the ROMs, meaning a customer had merely to buy an Apple ][ and immediately be able to Get Shit Done. It's possible someone else would have done it, and that they would've achieved the popular awareness to make it a successful product, but far from certain.
That said, if I were to point to something much more black & white, it would be something very closely related to Apple, but somewhat distinct: The 6502 CPU. In a time when even the cheapest CPUs cost hundreds of dollars minimum, the a $20 CPU was revolutionary, and it only happened because the Motorola 6800 team's was so insistent against management that it should be cheaper, when Motorola corporate ignored them, they quit and formed MOS to sell a 6800 clone at a fair price themselves. Here's a couple more points to consider: One, the first wave of 8-bit PC products using the 6502/Z80/etc barely existed in the 1970s, but the 68000 shipped in 1979, meaning if it was the M68k team instead that had revolted to form their own MOS Technologies, the 8-bit and 16-bit eras would've been bypassed completely! Two, while the first "integrated" (single-chip) CPU was the 1971 Intel 4004, the technology needed to create such a thing had existed since the mid-1960s, and the 4004 itself was only created as an incidental side-project in the development of another company's terminal console mainboard (which ended up using a discrete logic implementation, forcing Intel to look for other applications to sell the 4004).
The advent of the PC is very much an accident of history that could've happened decades earlier, later, faster, or slower.
Jobs (and Scully's after) anti-game disposition, and the Mac's b&w graphics (not to mention lack of A/V ASICs enforced by a legal settlement with The Beatles, no joke) certainly played a part, but the real killer was the lack of affordable developer tools. Early Macs were completely incapable of "bootstrap" self-development, relying on a >$10k Lisa for development, then when a native SDK shipped, it was the hundreds-of-dollars MPW, which further required hundreds of dollars of Inside Macintosh documentation. Other Mac SDKs like THINK C and Fantasm eventually shipped, they were still expensive and impenetrable for the time, amounting to too little, too late, for the sort of bedroom coders gaming relied on back then. While failure to ship a full Pascal/C/etc environment with the Mac was bad, far more harmful was the fact that no BASIC shipped with it. This was due quite substantially to Microsoft blocking the release of the (completely finished and ready to ship) MacBASIC developed by Apple, with the understanding MS would release a BASIC for the Mac, which they did (a disappointingly un-"Mac-like" product) far too late for it to matter.
As a result, it's unsurprising that the overwhelming majority of early Mac games were written in the only cheap rapid-development environment available, HyperCard. Which itself suffered from attempts by Apple to court 3rd-party devs by spinning it off into Claris.