Iginla was by far the most consistent goal-scorer out of all of these guys. He had the longest peak for sure and a very high peak at that.
I'm not sure if any of that is true. His consistency is based on his string of 30 goal seasons, which is great, but isn't an elite number, and is based on health as much as anything compared to most of these guys. In terms of peak, he only had 4 seasons in the top 10 in goals and none of them came consecutively. He was a consistently good goalscorer with spike seasons among the best. I'm not sure I would say that the extended period between his first and last top 10 finish is a "peak". Meanwhile, Stamkos was top 2 in 4 consecutive seasons and 5 of 6 years, and Kovalchuk was top 10 for 7 consecutive seasons.