According to Van's Aircraft,

3,862 RV aircraft have been completed and flown. By far the most
popular model has been the RV-6 model. Here's a table, by model,
showing number ever completed and flown, with accident statistics from
NTSB since 1/1/99 (the search looked for RV in the model designator
and excluded "incidents"):

Fatal accident
Model Flown Accidents Fatal Killed rate per year

RV-6/6A 1,850 68 13 21 0.15%
RV-4 1,127 31 7 11 0.14%
RV-8/8A 441 12 4 5 0.20%
RV-3 217 5 0 0 0
RV-7 114 2 1 1 0.20%
RV-9/9A 112 5 1 2 0.20%
RV-10 2 0 0 0 n/a

The RV-7, 9 and 10 are recent models.

By comparison, about 36,000 Piper Cherokee (PA-28) variants were
built. In the 1-year period up to 9/1/2003 there were 14 fatal
accidents in this fleet with 26 fatalities. This translates to a
fatal accident rate per year of just 0.04%. However, this large fleet
includes many airplanes built decades ago. It seems reasonable to
divide the "ever built" size by 2 to reflect the relatively more
recent vintage of the RVs. This still makes the Cherokee rate about
0.08%, significantly below the RV rate.

Of course, this doesn't provide the required comparison, which is to
sailplanes. Anybody got a reasonable estimate for the number of
sailplanes in existence, say, completed and flown since 1970?