Pins has nothing to do with it.
The SNES was based on a 16-bit microprocessor running a 21MHz clock with 128k of RAM. That's just the CPU. You'd still have to account for a GPU, Sound processor, and controller interface.
The Arduino is based on an ATmega328 which is a 8-bit microcontroller running 16MHz with 2k of RAM.
See the problem?