Adding on to what @pin142 said about queues, all rides have a capacity so the level of ridership is finite. This means you can't compare rides' popularity based on the number of people who rode it in 1 day. Another factor affecting that method is the amount of people who 're-ride' the ride. You know, those who hop off the ride and immediately re-join the queue. That would cause the data to be exaggerated.
A ride's popularity is probably best defined as the amount of people who want to ride it.
This is why, apart from the safety concerns, the closure of Thunder River Rapids has & will have such a negative effect on Dreamworld. Unless most people were visiting for a new attraction, that ride was the main reason people visited Dreamworld because they wanted to ride Thunder River Rapids. It was a universal ride.
Dreamworld consistently stated prior to 2016, Thunder River Rapids was it's most popular ride (and that opened in 1986!). Rocky Hollow Log Ride was always in 2nd place (and that opened in 1981!) but now clearly takes 1st place. It says a lot about the park that only 1 other ride since 1981 has opened that has proven to be more popular/universal than one of the opening day attractions. Usually, the more universal a ride is, the more popular it is. Simply, theme parks that cater for all with an attraction line-up that aligns with the diversity of their audience is successful.
Tower Of Terror II is a high thrill ride so the people who would ride this are usually thrill-seekers, a portion of the market. In short, Tower Of Terror II is not a universal ride as there are a lot of people who would not want to queue for this ride.
Tower Of Terror II not being the most popular/universal ride in the park is not a good reason to close it. However, in regards to using Tower Of Terror II's queue length as justification for a future closure, since it's carriage can hold 14 people, if the queue is less than 14 people long when they are loading the ride, then the ride at that point in time isn't currently sustainable to operate. That is, the ride does have “low ridership”. The ride should operate at times when they know there will be at least 14 people in the queue when they load the ride. If there are always fewer than 14 people in the queue when they load the ride then it is definitely time to stop the turbine.
However, it would be fine to keep operating it if it became an upcharge and/or with less seating and/or operating at certain hours of the day...or year.
So how many people still want to ride Tower Of Terror II?