Quite frankly, I think the people who think Mario had the best peak ever don't seem to show any understanding of the actual timing of the influx of elite European talent to the NHL. It strikes me as an argument of convenience to support their confirmation biases more than anything else.
Here's the entire list of European forwards who scored more than 500 points in the NHL, with their career point totals, sorted by year of birth:
1956: P. Stastny 1239, Nilsson 686, Gradin 593
1957: None
1958: Gustafsson 554
1959: A. Stastny 636, Naslund 634
1960: Kurri 1398, Steen 817, Larionov 644
1961: Sundstrom 588
1962: None
1963: None
1964: Sandstrom 856, Klima 573
1965: Tikkanen 630
1966: Pivonka 599, Kamensky 501
1967: Dahlen 655
1968: Bondra 892
1969: Fedorov 1179, Mogilny 1023, Khristich 598
1970: Selanne 1457, Zhamnov 719, Lang 703
1971: Sundin 1349, Bure 779, Nedved 717, Reichel 630, Rucinsky 612
1972: Jagr 1921, Alfredsson 1157, Kozlov 853, Straka 717, Palffy 713, Nylander 679, Stumpel 677
1973: Kovalev 1029, Forsberg 885, Naslund 869, Yashin 781, Holmstrom 530, Lehtinen 514
Summary:
9 from 1956-1960 (only 3 over 700 points, 3 HOFers)
8 from 1961-1968 (only 2 over 700 points, 0 HOFers)
24 from 1969-1973 (17 over 700 points, 7+ HOFers)
Key takeaways:
1. It is incredibly obvious that as a guy born in 1961, Wayne Gretzky had to deal with much, much stronger European scoring competition in the 5 year cohort ahead of him than Mario Lemieux (born in 1965). Lemieux's similar-age competition was actually almost completely non-existent, which defies the narrative in this thread about his peak coming in a supposedly so much more competitive league.
2. The group of European scorers born from 1961-68 was historically awful. These are players that were mostly age 21-27 in 1988-89, and 25-31 in 1992-93, meaning their prime years overlapped almost perfectly with peak Mario.
3. As a result, suggesting that the 1988-89 to 1992-93 period was significantly harder because of European competition really has no evidence to back it up. It's obvious that the 1969-1973 birth group of Europeans would change the NHL landscape forever, but that group wasn't making any impact at all in 1988-89 and even by 1992-93 was still very much on the upswing.
4. There were only 8 Europeans in the top 50 in scoring in 1992-93. Compare that to 9 Europeans in the top 50 in scoring in 1984-85, for example. Of those 8 in '92-93, 4 of them were in their age 21 or younger seasons, and 3 more were 22-23. In other words, the prime age European scoring talent in 1992-93 was an absolute black hole (as we'd expect from the breakdown by birth year above):
Europeans aged 24 or older in the top 100 in scoring, 1992-93:
37. Jari Kurri, age 32
57. Alexander Semak, 26
70. Nikolai Borschevsky, 28
71. Ulf Dahlen, 26
72. Michal Pivonka, 27
77. Dmitri Kvartalnov, 26
79. Thomas Steen, 32
5. On the other hand, all 9 Europeans in the top 50 in scoring in 1984-85 were born between 1956 and 1960, meaning they were all in their age 24-28 seasons.
6. There was significant turnover among European star players, especially elite Swedish players, around 1990 with stars like Loob, Naslund, Gustafsson, Sundstrom, Jonsson, Salming, etc. leaving the league, mainly because of the elite 1956-60 group aging out, or deciding to leave North America in an era where Europeans were more likely to return home early than they are today. It would take at least 4-5 years until the next wave made up for these losses, which again blatantly contradicts the oft-presented theory that there was a steady gradual improvement in the talent pool from 1980 to 1996.
7. The trend for elite American scorers was similar. There was an obvious wave of talent entering the league in the early to mid-'90s, but that group was still very much on the way up in 1992-93. If you look at the group of elite forward talent that would drive the 1996 World Cup success, for example, the only forwards on that roster older than age 22 in their 1992-93 seasons according to Hockey Reference were Brett Hull (28), John LeClair (23), Pat LaFontaine (27), Scott Young (25), Joel Otto (31) and Shawn McEachern (23).
That's a guy developed in Canada, a player who hadn't broken out yet as of 1992-93, one legit American-trained player who was an actual star in 1992-93, and three depth guys who all scored between 52 and 61 points in 1992-93.
8. Another often-advanced argument is that goalies were much better in 1992-93 than earlier, but I honestly don't see that much evidence to support that either. European goalies hadn't really made any significant inroads in 1992-93, that would only really start to happen in 1993-94. There was increased American depth, but there were also increased jobs from expansion. Potvin and Fiset had broken into the league as youngsters at the leading edge of the post-Roy Quebec butterfly revolution, but the rest of the troops hadn't yet arrived. Once again, people seem to be treating 1992-93 as equivalent to later seasons with the international talent pool had both deepened and matured.
9. The only areas you could maybe make an argument about a significant increase in depth from European players is among second-liners and second-pairing defencemen, but is that really what we're talking about when we talk about a much stronger league? That also has to be adjusted for in the context of there being extra jobs available from expansion.
10. In summary, while it is fair to say that there was some increased depth in 1992-93 because of the influx of Americans and Europeans, that impact is massively overrated because it doesn't account for how young most of the key players still were at that point in time, as well how much of a hit the league took in terms of elite import talent in the late '80s as the elite 1956-60 European cohort moved on without being replaced because the 1961-67 group was so weak.
If you're going to try to promote Mario's peak as the greatest ever, at least try a good argument rather than some vague gesture to international talent pools. The reality is that Mario's peak was actually perfectly timed to exploit the worst cohort of elite European scoring talent in modern NHL history.