WC is really a small size sample for making such claim. Its like taking less than 0.1% of the total goals/games played back in those time, which makes it really negligible when we are comparing general stats of the games across eras.
Well obviously its difficult to compare how big the difference was between those past eras and now. But I have seen more strikers getting ridiculous high goal ratio back then as compared to modern times. I think this says something.
Do you think it's a far stretch to claim Muller has been better at WC's and EURO's than Ronaldo?
Muller:
WC: 14 goals (1 penalty) and 6 assists in 13 games - 1 gold and 1 bronze in 2 championships
EURO: 4 goals in 2 games - 1 gold (strange 4 team format) in one championship.
West Germany scored 35 goals in those 15 games (2,33 goals/game) and Muller was directly involved in 24 out of their 35 goals (69%)
He also scored or assisted in every KO game he played for West Germany.
CR7:
WC: 8 goals (3 penalties) and 2 assists in 22 games - best finish 4th place - 0 goals or assists in 8 KO games in 5 WCs
EURO: 14 goals (3 penalties) and 9 assists in 24 games - 1 gold and 1 silver - in 5 EUROs
Portugal scored 71 goals in those 46 games (1,54 goals/game) and Ronaldo was directly involved in 33 out of their 71 goals (46%)
Muller scored more non penalty goals in WC and EURO in 15 games (17) than Ronaldo has done in 46 games (16).
You are right that West Germany scored more goals per game in the big championships in the early 70's than Portugal has in 21st century though.
There weren't many others than Muller putting up rediculous numbers in the late 60s and early 70s though. The 20's, 30's, 40's, 50's and early 60's was different, but it was also different form country to country though. Pele (Santos scored on avg. between 3,5-4,5 goals in the Paulista in the late 50s and early 60s and had double digit hauls on multiple occasions in the league in that period) and many others had great working conditions in semi professional leagues. Peyroteo scored 332 goals in 197 games in the Portoguese top flight and 544 goals in 334 games in all comps between 1937-1950....(an average game in the Primeira back then had 5+ goals)
Playing for dominant, high scoring teams is also a very important factor for putting up huge numbers though.
Barcelona and Real Madrid between 2008-2018, Bayern 2017-2023, City 2017-2023 and PSG 2015-2023 has provided the best working conditions a goalscorer could have in the last 60 years. Real Madrid and Barca has both had seasons above 3 goals per game, while the others between 2,5-3 goals per game. Bayern has scored 3,82 goals per game so far this season so be prepared for a potential record season from them and or Kane.