When I speak to people about coasters, especially people who are older then me, or have no interest in coasters, 3 names are always mentioned,
The Big One, although, nobody ever calls it by that name, or PMBO, most people I have spoken to about it know it as simply "Pepsi Max"
The others are actually Corkscrew at Alton Towers and the Scenic Railway at Margate.
But as far as famous goes, to claim to be famous a ride must have world wide acclaim and or some kind of worldwide relevance for a long period of time, it would be a ride from a time where a trip to a theme park meant more then it is now, so parks like Alton Towers, Blackpool and obviously Disney etc. Nothing built recently can really be heralded as famous because there's just to many coasters and park springing up all over the place these days that people forget them, maybe in 10,15 years one or two may classify as famous, we will see.
That in mind, I like The Big One, it really set the bar for what could be achieved with coasters, I think the world must have stood up and taken note way back in 1994, it would have been and still is a monumental sight, configure that with it being located in a holiday town where not everybody comes to the town to ride rides, it really would have been or at least should have been very famous.
Others include Space Mountain, Cyclone and possibly The Beast and Nemesis?