There's actually more to the story about the 6502 than that. The 6800 series (except for the 6809) executes all instructions in four clock cycles. The 6501/02 and subsequent members of the family executes them in one cycle. Clock for clock, MOS Technology processors and their derivatives were four times as fast. Same thing with 68000 vs. 65816. If it wasn't for that stupid page memory addressing system, it would have been another hit out of the park.