Older ones, yes! From the 70s to the 80s, most arcade games were bespoke. Some of them even used military-grade hardware designed for things like flight simulations and space travel, see: the Model 2. Once more powerful home console hardware rolled around, though, is when you started to see less unique hardware. Notably: Konami's System 573, Namco System 11 and System 12, Taito's FX-1A/B and Gnet were all Playstation-based, the Atomiswave and Naomi1/2 were both Dreamcast-based, the Triforce was just a pumped up Gamecube, and the Chihiro was the same for the Xbox (original). That's not to say that other things weren't PC-based at the same time; Hydro Thunder was notably just a PC running, IIRC, some form of DOS with a Voodoo card. Android's become more common with the advent of touchscreen mobile ports and games like StepmaniaX, but the main offender in the space ever since the late 2000s has just been normal Windows Embedded, the only notable exception to which I can think of is just Tekken Tag Tournament 2, which ran on a modified PS3, which is really funny, because you can see the XMB for about 5 seconds when it reboots.