Completely different graphics hardware, the C64 used the VIC-II, and the NES had a custom Picture Processing Unit (PPU) developed by Ricoh, among other things.

Completely different graphics hardware, the C64 used the VIC-II, and the NES had a custom Picture Processing Unit (PPU) developed by Ricoh, among other things. The CPU is only a small part of a larger design, and 8-bit computers were created before any kind of standardization arrived.