It doesn't really make sense to use "bytes processed per second" as a metric. Even if it did, it's not even clear what "8-bit" means for the 6502 - it had an 8-bit accumulator and two 8-bit index registers, but a 16-bit address bus and multiple 16-bit addressing modes. Opcodes can be one or two bytes.
I am not as familiar with the 68000, but I know it's a RISC CPU - a rather different architecture, it has a lot more registers, and going by Wikipedia, 16 32-bit registers (8 general-purpose registers and 8 address registers, one of which served as the stack pointer, as opposed to the 6502's one accumulator, two index registers, a program counter, a stack pointer and flags register). The address bus was 24 bits (meaning it could address up to 16 MiB of memory instead of the 64 KiB available to the 6502).
The 68000 was much faster and more powerful than the 6502, but newer and more expensive as well. Unfortunately there is no perfect (or, arguably, even good) way to easily compare completely different processor architecures using one number. Attempts at constructing synthetic benchmarks like the Dhrystone score tend to be flawed in somre respect.