Since we are past the silly bickering stage, let’s try to start in with an answer to the question. Although it was intended more generically, let’s use 1970 as at least 1970 was a decent vintage; this would be easy if we were using, say, 1972. Using Parker’s ratings on 1970 as a proxy (people with different experiences can substitute theirs) and politely including Mouton Rothschild as a first growth, although it didn’t get that rank until 1973:
Haut Brion: 85
Lafite: 85
Latour: 98+
Margaux: 76
Mouton: 93 (described as “irregular”)
If we want to use 1982, a great vintage, we see:
Haut Brion: 94
Lafite: 100
Latour: 100
Margaux: 98+
Mouton: 100
Or 1990, another good vintage and long enough ago to see some effect of change:
Haut Brion: 96
Lafite: 92
Latour: 98
Margaux: 100
Mouton: 87
So to compare the second growths in 2016 to the first growths. These are my opinions; others can chime in: that was the point of opening the discussion. (NB: the comparison for the first growths is sort of an average; for instance, nothing is going to beat 1990 Margaux or 1982 Latour, but I didn’t want to type that every single time.)
Rauzan Segla: Much better than 1970, not as good as 1982, almost on par with 1990.
Rauzan Gassies: Maybe better than 1970, not in the same league as 1982 or 1990.
Leoville Las Cases: Much, much better than 1970, on par with 1982, better than 1990.
Leoville Poyferre: Much, much better than 1970, nearly on par with 1982, better than 1990.
Leoville Barton: Much better than 1970, close but not quite as good as 1982, on par with 1990. Also a good value.
Durfort Vivens: Better than 1970, not as good as 1982, not as good as 1990.
Lacombes: Better than 1970, not in the same league as 1982 or 1990.
Gruaud Larose: Much better than 1970, not as good as 1982 (maybe not as good as its 1982 counterpart), on par with 1990.
Brane Cantenac: Much better than 1970, not in same league as 1982 or 1990.
Pichon Baron: Much, much better than 1970, nearly on par with 1982, better than 1990 (maybe not as good as its 1990 counterpart).
Pichon Lalande: Much, much better than 1970, nearly on par with 1982 (maybe not as good as its 1982 counterpart), better than 1990.
Ducru Beaucaillou: Much, much better than 1970, nearly on par with 1982, better than 1990.
Cos d’Estournel: Much, much better than 1970, close but not quite as good as 1982, on par with 1990. Yes, I am aware the 2016 received 100 points from the WA.
Montrose: Much, much better than 1970, on par with 1982, better than 1990 (maybe not as good as its 1990 counterpart).
Because this was a lot of work, I’m skipping to the fourth growths.
St Pierre: Better than 1970, not as good as 1982 or 1990.
Brainaire: Better than 1970, not as good as 1982 or 1990.
Talbot: A little better than 1970, not in the same league as 1982 or 1990.
Duhart-Milon: Much better than 1970, not as good as 1982 or 1990.
Pouget: No idea, so probably not as good as anything back then.
La Tour Carnet: A little better than 1970, not in the same league as 1982 or 1990.
Lafon Rochet: Better than 1970, not as good as 1982 or 1990.
Beychevelle: Much better than 1970, not as good as 1982, close but not as good as 1990. Unclear if the 2016 was an exception or they can sustain the quality.
Prieure Lichine: A little better than 1970, not in the same league as 1982 or 1990.
Marquis de Terme: Better than 1970, not as good as 1982 or 1990.
Several of the fifth growths have clearly moved up in the ranks, so highlighting them.
Pontet Canet: Much, much better than 1970, nearly on par with 1982, better than 1990.
Grand Puy Lacoste: Much, much better than 1970, close but not as good as 1982 or 1990 (maybe not as good as either its 1982 or 1990 counterpart).
Lynch Bages: Much, much better than 1970, close but not quite as good as 1982, better than 1990 (maybe not as good as its 1990 counterpart).
HTH.