To reiterate, just because Koroliov is on a label without good circulation in the US, doesn't mean he's an obscure Bach pianist.
To give some examples,
Aside from the two critics at Classics Today, Distler (who also writes for Gramophone) and Hurwitz.
His Book II and Goldberg variations each received a Diapason d'Or.
His Art of Fugue was editor's choice in Gramophone.
And of course, there's that famous quote from György Ligeti, who is one of if not the greatest composer of the 2nd half of the 20th century.
Unfortunately, however, he has been overshadowed in the markets by Schiff, Hewitt, and Perahia. Perahia, of course, has done the Partitas and English suites, which Koroliov has not recorded. Schiff is a mincing pianist in everything, and he screws with the counterpoint in Bach. Hewitt is too timid, genteel, and bird-like for me at least. Just because they have been more heavily promoted, and have a politely appealing sound, does not mean they are on the same interpretive level