Quite different, by try "porting" NES games to a modern CPU, for example using zero page instead of just doing operations between registers that more modern CPU

Quite different, by try "porting" NES games to a modern CPU, for example using zero page instead of just doing operations between registers that more modern CPUs allow unlike the 6502. Different programs from different times were made with different assumptions. It's much easier to emulate (and they games will actually run correctly).