McDavid of two years ago vs. 1927-28 Morenz is a chestnut that might have to wait for my afterlife to be able to crack. Morenz had the best pre-Howe Regular Season. McDavid seems to have had the best post-Lemieux Regular Season. Will a McDavid season be the greatest season of the half-century 2000-2050? I'll probably assume ambient-air-temperature before that answer is clear [unless McDavid or somebody else uncorks one for the ages and visits peak Gretzky territory before then].
Hot take: even granting Hasek the generous allowance of disregarding The Playoffs, is his 1997-1998 clearly better than Bernie Parent's 1973-1974?! A few years back, I synthesized a "Save Percentage vs. 3" stat as kind of an imperfect Goaltender parallel to VsX. Doubtless it would benefit from some fine-tuning by a stats-wiz... but I STILL like it (flaws & all) over "Goals Saved Above Average," for instance. [Third highest performance-rate among Goaltenders in-the-league seems a more stable measuring-stick than average Goaltender in-the-league... which during Plante's time would be somebody like Harry Lumley, and during Parent's time would be like the much less-regarded Eddie Johnston, and during Hasek's time would be, like- Andy Moog territory.]
In 1997-98, Hasek was in 72 of 82 games, his best "strike-rate" ever. (This superior games-played rate is why I consider this to be his best season- over the higher save-percentage rate 1998-99.)
1973-74 Parent appeared in 73 of 78 games.
Hasek's .932 Save Percentage is good for a "Vs3" of 1.011. Anything over 1 means typically means that you're either a strong 2nd place, or (as in these cases), a league-leader. The ".011" is statistically significant... it's 21 less goals on the scoreboard than 97-98's third place rate would have gotten you. [Assuming a 30 shot-per-game/70 starts-per-season paradigm, which (based on a quick-and-dirty glance) appears to be a slight overestimate of shot-volume that year.]
Parent's identical .932 Save Percentage is good for a "Vs3" of 1.025. Applying the same constants, this is 27 fewer goals than would have been yielded by that year's third-place performance.
So... comparing 1973-74 Parent to 1997-98 Hasek:
Parent played more games, a higher percentage of games, stopped pucks at the same rate, and outperformed most of his higher-level peers by a greater margin. How can we conclude he did worse, that year?!?