This one's actually not that easy. Selanne's got that really awesome 76 goal rookie season that won't be beaten in several lifetimes. He's also got a few 100+ point seasons in his career. While most of his gaudy offensive totals are due to his own talent and skill, I do think Selanne was also helped out more by the players he skated with - Paul Kariya in particular, was awesome in his prime and they had a ridiculous synergy together. Phil Housley in his rookie year is nice too.
Iginla, on the other hand, has a scoring title and a couple of Rockets. His overall scoring totals are lower than Selanne's. Some allowance must be made for his prime coinciding with the dead puck era (whereas Selanne did miss some of it early on in his career), and skating with lesser linemates. Iginla had more leadership qualities and was more intimidating (a decent fighter).
I personally prefer Selanne, but in this comparison I will give the slightest edge to Iginla. Iginla is practically equal in scoring with a more complete game. Honestly, I'd be happy with either one of them.
My issue with his rookie season, as incredible as it was, is two-fold (from an historical point of view):
1. Goals were easier than candy at a parade that season. Wasn't that the highest scoring season in NHL history? Even though Teemu scored 76 goals, he wasn't even the clear-cut goal leader that year (he was tied with Mogilny). In fact, there were 14 players with more than 50 goals, and five players with more than 60! I got awarded eight goals just by attending 20 Jet games that season.
Meanwhile, Iginla was scoring when nobody else was. A two-time winner of the Richard Trophy, he was 11 goals ahead of the second highest scorers during his 52 goal season.
2. I never consider players who have already played in a pro men's league true rookies. He was already an established goal, mature 22 year-old goal scorer when he scored 76 goals (Laine, as a comparison, won't be that old for two full seasons yet). I find Bossy's rookie record more impressive because he was straight out of junior.
Hey, I don't want it to sound like I'm dissing Selanne. He was incredible, and was easily the best Finn to ever play the game (sorry Jari). I just find that we're comparing two very different goal scorers, and Iginla never had a chance to play in the high scoring era that Selanne began his career in.
I'll concede that Selanne was a more impressive pure goal scorer, but Iginla's leadership, physical play along with his offensive output on some weak Calgary lines should not be ignored. Plus, I'll always insist that he should have won the Hart over Theodore and the Conn Smythe was his if Calgary's Stanley Cup wasn't stolen over the Gelinas goal that didn't count.