The 6502 is the chip used in a lot of things, IIRC the Apple IIe among them. The real significance of the 6502 isn't that it's the NES chip but that it's a superset (instructionwise) of the 6507, which was in the 2600 and I believe the first microcontroller of its kind. A truly revolutionary piece of technology.

BTW, calling the 6502 a CPU is a very generous name... it implies that the chip can do a lot more than it can.