This kind of bias :
That nation’s history isn’t particularily illustrious… Not any more than any other european nation. It had times of glory and times when it was pretty much irrelevant. Actually its time of glory was the 19th century. Period.
Concerning generals, the british army was rather less often involved in wars than continental nations, for obvious reasons. So, yes, there’s a non insane reason why there should be less succesful british generals. Simply because significantly fewer british generals fought any war at all. Sweden or Poland, for instance, though not often mentionned, probably fought much more wars and battles than the british army. Austria has been an “illustrious” nation too. It has been involved in countless conflicts with pretty much everybody in Europe. So, wouldn’t you expect at least some Austrian generals to make it to such a list?
I don’t remember the british army having ever been considered as particularily famous, remarkable or feared until the 20th century, actually (contrarily to, for instance, the spanish tercios, or the 18th century prussian army). Only the british navy has been illustrious, and this only since the late 17th - early 18th century.
And yes, I think it’s directly related to most posters (americans, canadians, australians…and of course british) being much more conversant with british history.
I could list a large number of french generals whose names would probably rings no bell for most posters, in the same way the name “Wolfe” would probably got you a blank stare if mentionned to a random french person (actually any british general except for Wellington and maybe Malborough due to a silly children song would probably got you a blank stare) . The british army being mentionned rather than the prussian or russian one is, in all likehood, not due to its history being particularily “illustrious” but rather particularily familiar…