There is no universal judgement of how advanced a rider is because there is no universal way to ride a horse - look at the US Pony Club and how much trouble they're having with their rating system just for English riders. Can you imagine how hard it would be to throw western riders into the mix as well?
The problem is that people can be good at different things because they have focused on what they enjoy at the expense of some other aspects. To use myself as an example - I am a pretty experience flat rider, I have done it for 20 or so years and can get horses to do what I want the vast majority of the time and teach them how to do things they don't know or haven't learned. I've riden hundreds of horses over the years (mostly on the flat), good ones, bad ones, young ones, old ones, and fallen off a good number of them
. I've ridden a little bit of western although with Aussie stock tack rather than the full western gear but I do own a pair of cowboy boots
Now, I haven't done a whole bunch of jumping recently. I competed when I was young and then decided there was other stuff to do and never went back. I can still ride a horse over a jump but there is no way I would consider jumping anything but an experienced and easy horse, whereas I will ride absolutely anything on the flat. My discipline of choice has been polocrosse in which horses stop, turn and accelerate very very fast which takes as much skill as jumping, just skills that are somewhat different.
I regularly swap tips with an eventer at our barn, even though we ride very differently so there is some overlap.
My basic point is this - there is such a range of activity that you can't judge peoples ability to ride against one universal standard, you have to look at them in relation to their chosen discipline, which means you can't really judge (for example) an eventer against a polo player because there is no one universal standard.
My final point - riding experience is measured in years, not hours. If we were able it would probably be measured in lifetimes.