Convid-19 is very similar to SARS in that both are Coronaviruses. SARS had a higher mortality rate but didn’t have the “fitness to persist in the human population,” which eventually led to its demise. Also SARS had symptoms that were severe and therefore easier to identify and contain.
What makes Convid-19 so unique and potentially deadly is that so many people had mild symptoms or are asymptomatic and therefore don’t see a doctor and are largely unaccounted for. The rate of spread can potentially be a lot more higher.
N1H1 as Sparty mentioned had a reasonably large rate of spread, though the mortality rate was marginally higher than the regular flu. The reasoning was it effected the population more under age of 60. One third of the population over 60 already had antigens to combat this flu, and with a younger and stronger patient-base the mortality rate remained low.
I have heard the term "senior killer" with this virus and the stats seem to prove this unfortunately. The early mortality rate for anyone over age 70 is around 10 percent.
In the end, all these pandemics are unique in that they effect the population differently. Yes, in hind site some seem minor but eventually we will have one similar to the 1918 Spanish Flu. My thoughts are do what you can to minimize the effect.