comparing sakic to the twins, yes, sakic was a far superior player. he's one of the greatest players of all time. and comparing his historic season (I believe still the oldest player to ever hit 100 points?) to the sedins before they peaked seems like a fairly disingenuous comparison.
selanne is an interesting example too, since it's no coincidence that his rookie year was by far his best. as the league got better around him, he stood out less. in fact, you should check any of those 90s greats and see where they peaked. of course production will (almost) always decline with age, but compare sakic's numbers from the 90s to his numbers in the 00s. he put up way more points in the 90s when the league was worse than he did in the 2000s, even when he was still in his prime competing for cups.
the top end talent wasn't better, but the rest of the league was worse, which made them look better. the gap between elite and average was huge whereas now it's small. back then, guys who were doing offseason training and paying attention to fitness and nutrition and doing skills development were the exception, only the elite who were looking to set themselves apart. now every 14 year old who has even the slightest dream of playing in the league is doing those things.