Pagetable.com has in interesting post about emulators, specifically one created in 1978 to run Intel 8080 code on a 6502. While emulators today are fairly common, such as running Nintendo (6502) games on a PC, or In Circuit Emulators for development, an 8-bit cross architecture emulator is certainly different. Especially since the 8080 and 6502 were so vastly differing. Certainly a useful tool for teaching oneself a new architecture, and as they were coming out rather rapidly in the 1970’s knowing more then one was a worthy investment.
Todays equivalent perhaps would be emulating a PIC on a 8051. Perhaps someone will give it a try?