It's hard to do rankings partly because some players had 1-2 incredible years, while others may have had a longer and more consistent prime but maybe not the glamorous numbers as someone with short prime.
All I will add is that Mario should be undisputed #1. Gretzky belongs on the list. I'll make room for mogilny and selanne because they had the best single season scoring numbers. Hull belongs there too as probably the best scorer of the 90s overall. Lafontaine at one point was arguably the 2nd most dangerous forward behind lemieux, so he belongs somewhere. Lindros was the most dominant player at one point in the 90s. Finally, iginla scored 500 goals and he did most of that in an unfriendly era for goals, which is incredible.
I mean, we can go forever on this topic.... there's so many I've left out still, and I'm mostly just focusing on goals.