Most good analysis try to compare activities hour for hour. So how risky is an hour of motorcycle riding vs an hour of Gliding. This is done to as much as possible eliminate the issues pointed out about the frequency of the activity or the number of people doing it.

Most of the analysis I have done and observed seem to indicate the GA Aviation over all is has about the same risk as riding a motorcycle hour per hour. Gliders seem to be a bit worse. But as with motorcycles there are riskier kinds of activities that get lumped into the over all numbers like Low thermalling, flying in bad weather, Low finishes. So even with the overall number you can individually improve your odds depending on what kinds of risks you are willing to accept.

Brian
CFIIG/ASEL