Ziggy Stardust said:
Let us not forget, Darth was in the prequels.
True.
It would be interesting to somehow find a way to measure if the recognition of Vader by those 14-year-olds was from the OT or the PT. My guess would be that it's a combination of both. For 34 years Vader has been a cultural icon of bad. That's fame the prequel characters can't buy.