1. Ilja probably belongs in his own category. He is substantially stronger than the other European amateurs at this point. He's currently 84 points ahead of Antti at this point. Here is one estimate of win rates, though it seems to be based on Chess: (
http://senseis.xmp.net/?Gor)[1]. If you speak of amateurs in the plural, it is relevant how Ilja does, but doesn't suffice. So with regard to each group of professionals, we should distinguish three claims: "they are better than all European amateurs", "they are better than all European amateurs but Ilja", and "several European amateurs either have parity with them or are stronger."
2. European ratings are wonky when professional ratings come in to play, but it does seem that Taranu is not as strong as he used to be (
http://europeangodatabase.eu/EGD/Player ... y=10586785). The same is true for Dinerchtein (
http://europeangodatabase.eu/EGD/Player ... y=10313237
3. Almost all your positive evidence concerns non-Chinese/Korean professionals. I continue in my contention that it is quite clear that they are stronger than European amateurs. Search for the top players by Gor on the European database and look at the flood of > 2700 Korean amateurs, or consider this tournament for suggestive evidence (
http://europeangodatabase.eu/EGD/Tourna ... n=16250014). I realize that this paragraph does not contain dispositive evidence, but if you seriously wish to dispute it, I could compile more.
4. So that leaves the Japanese and Taiwanese professionals. The case is more equivocal here, and there's has been a lot fewer head to head encounters, unfortunately. I'll try to come back to it (and of course this means that I haven't fully refuted you).
[1] Good question for someone who knows: are those numbers accurate for Go? Is there a good estimate out there?
Edit: changed "less competition" to "fewer head to head encounters" for clarity.