Sholay is the biggest hit in the history of Bollywood, being the highest grossing film of all time in Indian cinema, having grossed around US$160 million. In 1999 BBC India declared it the "Film of the Millennium". A Royal Enfield features prominently in the movie.
Update: Or so I thought. Many places claim that the motorcycle is a Royal Enfield. In fact, the actors reenacted part of the scene recently on a Royal Enfield, however, following the comment by Mr. Shiv, I researched the issue further. The video is not clear enough to see, but in this picture, it appears that the motorcycle is NOT a Royal Enfield.