Nessie was the first and is now the only. The only other was was Orient Express- Lightning Loops didn't count.
Now this is why I believe that Nessie won't be leaving for a very long time.
1. Nessie is by far the most loved coaster in the park. If they announced the removal of Nessie for no good reason*, I can almost assure you that there would be mobs of people [including me] trying to save it as well as an out-cry from the coaster community like we have never seen before.
2. With the refurbishment that it received over the winter, we see that BGW is still willing to put time, money, and work into their oldest coaster.
3. Awards. When it was built, it was the tallest coaster in the world. It was the first with interlocking loops. It is now the only with interlocking loops. Its trains have traveled farther than any other coaster's trains on this planet.
4. It is an ACE Coaster Classic: http://www.aceonline.org/CoasterAwards/details.aspx?id=40 [That isn't one of those things that every coaster gets]
5. The park has stated that they don't see any better use of the land. Think about it: When Nessie was built, she was built to fit the terrain. Over the years, the park itself has been built around her. Trying to build a different coaster into the area that Nessie would leave would be near impossible.
6. This picture and the thousands of others like it symbolize the park. When you show that picture to anyone in the coaster world, they can instantly tell you what it is. This picture shows the park for what it truly is.
Picture from the RCDB
*A good reason would be a natural disaster, injury, death, etc.
