... What I would take issue with is the inference that Morphy's opposition was lacking. In fact they were the standard of the times. What else could they be?? Morphy's opponents were different than those today because the mid 19th century wasn't the 21st century. So the really real question should be why Morphy wasn't more like his opponents (as he should have been), not why his opponents weren't like the ones today (which they could never have been). Fine, in his Psychology of the Chess Player, would criticize a Romantic player for his lack of positional considerations , ignoring the fact that positional principles hadn't even been developed in Anderssen's time and were only a vague notion. It's this type of anachronistic reasoning that I take issue with.
I don't know who has been asking "why [Morphy's] opponents weren't like the ones today". I quoted from a GM Reuben Fine book that is, to a large extent, an account of the progress of chess. I did not quote from The Psychology of the Chess Player and would not want to comment on a statement in it without seeing the actual quote. Again, in book after book about Morphy, I have not seen disagreement with what I quoted in #397.
... He played 5 serious matches. The ones vs Löwenthal, Anderssen and Harrwitz are obvious. His match vs de Rivière was to fulfill promise, but de Rivière, the best French player of his day, is often more underrated than he deserved. Morphy's fifth match was with James Thompson at knight odds. This match is often dismissed as a variant, but that denies the reality of chess at that time.
Löwenthal, a voice of chess during that period expressed, "I am decidedly of the opinion that his [Morphy's] winning the match at the large odds of a Knight to a player like Mr. Thompson, is the most marvelous feat which ever a master of his rank has performed. Neither La Bourdonnais, M'Donnell nor Philidor could ever have accomplished a similar task."
Interestingly enough, Karparov had some misgivings about his pawn and move match with an IM (Terence Chapman), rated 600 pts. lower. Although he was successful, I think it demonstrates, first, the exquisite abilities of modern chess players whereas such a rating difference translates into such a minor handicap and second, the extent of Morphy's dominance over his peers. ...
I have not seen any authority say that de Rivière was anywhere near Löwenthal, Anderssen, and Harrwitz in playing ability. I have not seen any authority say that one gets good rating data from games at odds or from games against very inferior opponents.
What "rating data" ? There were no ratings back then. But in comparing chess players, odds was indeed a measure commonly employed.
I can't say *how* strong de Rivière was, but he was stronger than most people seem to assume. Was he stronger than Löwenthal? I don't know but here's the two times they met OTB- http://www.chessgames.com/perl/chess.pl?pid=19545&pid2=31145
Here he is vs Harrwitz- http://www.chessgames.com/perl/chess.pl?pid=15956&pid2=31145
... and vs Anderssen- http://www.chessgames.com/perl/chess.pl?pid=10342&pid2=31145
I'm no authority but they look pretty darn close to me:
de Rivière vs Löwenthal +2-0
de Rivière vs Harrwitz +1-2
de Rivière vs Anderssen +5-4=1