Basically, anything with a program sophisticated enough (and has some way to receive virus, display and sound wouldn't work) can be virused.
Storage and BIOS (GPU's have BIOSes called VBIOS as well) can be hacked, therefore the most common is the OS in the storage, since when you get a foothold in the OS you can use all the hardware as you like. This makes the OS #1 target.
CPU is infeasible to hack, since the data in it gets refreshed frequently, and the microcode(firmware of the processor) is too small to carry a virus. Don't mix CPU vulnerabilities like Meltdown and Spectre to CPU viruses, they are vulnerabilities which lets malware to bypass security towards your OS and CPU is a bridge here.
GPU's can be hacked, but it's not so...