Pronto,
I'm pretty sure that the relative statistical risks for motorcycling and private flying can be ascertained.
There is a "Statistics Year Book" published by the National Statistics Office I believe. It is a HMSO publication and is almost certainly filed in the reference section of your nearest public library. It contains abstracted statistics ranging from household expenditure on bog-roll through to %GDP derived from maggot farming (I might be exagerating a little here)!
I'm betting that Bookworm has a copy of it at his fingertips.
It does however list the total number of vehicle miles travelled per year by cars, lorries, motorbikes, etc, and the numbers of the various types of each licence held in the UK. It also lists road casualties per annum again subdivided into various catagories (including motorcycle fatalities). By combining all this information you can start to derive statistics for %of all persons holding a motorcycle licence who were killed or seriously injured last year, or that a motorcycle fatality occurs every xx,000 miles etc.
It is all very sobering stuff & from memory the frequency of fatalities (per mile travelled) for bikers was about 15 times that of car drivers. (Pedal cyclists and pedestrians also came out badly by this measure).
It didn't contain any stats for private aviation, only info for scheduled commercial flights (passenger numbers, etc.), but I should think that the CAA or AAIB websites (or for that matter the FAA or any other regulatory collector of statistics) would be able to provide comparable figures - (doesn't GASIL publish an annual death toll broken down by fixed wing, rotary & microlight types, together with the "one fatality every xx,ooo hours" figures)? - I seem to recall it is about 1 fatality every 60,000 hours for fixed wing.
Anyway, raw statistics, whilst useful for comparison purposes, can hide a lot of devil in the detail. And as FNG points out, an individuals risk management can affect their personal risk by a considerable magnitude either side of the published averages.
Personally, as someone who often motorbikes to and from the airfield to go flying, I often amaze myself that I make it home in one piece at all! (I'll probably get run over by a number 11 bus on my stroll to buy a newspaper now)!
Perception of risk is highly subjective, but I would say that my own gut feeling is that the two activities seem broadly similar in risk profile. If anything, motorbiking seems slightly riskier but that is perhaps due to my inability to have control over the myopic drivers alluded to by FNG, and thus manage this risk effectively.
Mr. W
P.S. I think I'll have a lie down now & give buying the newspaper a miss - you can't be too careful.