All it took me to stop was the imperfect emulation of the games I liked compared to the actual games, as well as the opening of a retro game shop that sells so many of my old favorites. Getting an actual job (and hence, money) helped, too. I don't think I could ever go back to emulation.... it's a pain to deal with, especially all the time and money I've spent on building a great "gaming corner" and library with old systems. Just turn on the TV, put in the cartridge, and bam, good to go.
Plus, I want to actually support developers for old games, when applicable. Many of the old games have current releases (Wii virtual console, and the amazing Sonic CD port, for example), and I didn't buy them back in the day.