Given the discrepancy, I'm guessing there might be multiple sources for such quotes from and/or about Lem. Not that the phrasing makes a huge difference, most Science Fiction being American Science Fiction.
In fact upon further reading, it seems to me that the quote(s) originate from material that was originally in Polish, then translated (among other languages) to German, then from the German
adapted (i.e.: translated/edited liberally) to English. (see:
http://www.depauw.edu/sfs/backissues/14/lemaffair14.htm)
But what's the eye-roll for?
If nothing else, I have difficulty disagreeing with Lem's assertion that most science fiction is poorly written. Comments about two and one dimensional characters well illustrate that some of the genre's greatest achievements are subpar in some literarily fundamental ways. (Despite obviously excelling in other ways generally considered more important to the genre, but which ought not impair literary fundamentals.)
As to your dismissal of him on account of never having heard his name before... I'm left a little astonished.
- Ahi