I admit to being somewhat of a "data junkie" myself, and for years have carefully poured over the data tables in Road and Track as well as the various motorcycling publications I read regularly.
I would note that even with cars, some of this is relatively usless data. This seems to be more the case as the handling of modern cars (at least as measured by the statistics) has gotten so much better. When R&T first started including skid pad figures in their tests, a production car that could generate 0.72 g was considered very good. Improvement in tires, suspensions etc have resulted in nearly all cars turning in stats much better than that.
For example, in 1974 I had a Datsun (Nissan for you who are too young to remember when it was called Datsun) 260Z. If I remember, per R&T, it cornered at 0.72g. A couple of years ago I had a 4X4 Chevy pickup, that, according to Motor Trend, cornered better than that (I don't remember exact stats). Now, I concede that the Chevy was a reasonably good handling truck, and also that my memory of the mid 70s could be somewhat clouded, but I am pretty certain that the Z handled far better.
I now drive (when my wife lets me -- it is really her car) a 1999 Mazda Miata. Subjectively, this is one of the three best handling cars I have ever driven (the other two being a Fiat X-1/9 and a Lotus 7), an impression shared by many professional road testers. However, based on skid pad results, there are a number of Toyota sedans that would beat it.
To quantify motorcycle handling in a meaningful way would be even more difficult. Fact is, given a nice big grippy surface with lots of runoff in the event of a crash, ultimate cornering speed for most production bikes is limited by cornering clearance, and how far the rider can hang off. Not only would a measure of maximum Gs be difficult to measure, it also would not give much meaningful information about a bike's handling, even on the track.
Even more so than with cars, bikes seldom spend any time at constant cornering mode (125 gp bikes might be an exception) -- they are braking deep into the turns, usually almost to the apex, and almost immediately past the apex, the rider is starting to roll on the throttle. It is the bikes ability to corner and brake simultaneously, or to accelerate and corner simultaneously, to provide the best feedback to the rider so that he/she can find the limits that makes a great-handling bike.
Braking is another problem area. Stopping distance from a given speed, whether for a car or a bike, is increasingly meaningless. At best, it is a measure of what might happen in a single panic stop, assuming that you have perfect reflexes and skills, and that you don't actually panic. It says nothing about feel, feedback or fade resistance. If you evaluate R&T data pages, you will note that the car with the shortest stopping distances often do not get the "excellent" subjective ratings.
It would be very helpful if there were a way to measure and quantify the factors than make a bike handle well or stop well. I am pretty sure that the technicians for the MotoGP teams at Honda, Yamaha, Ducati etc have some pretty good data for such evaluations. I am equally sure that the telemetry used to measure this is outside the budget of even the best-funded magazine, and that the methodology they use is a closely guarded professional secret.
Regards
Bob