Semin lacks the mental tenacity and makeup to be on Evgeni's level.
I see what you're saying, but that's a fallacious statement because you don't know him personally, are not his coach or his shrink. Nor do you have any (presumably) personal connection to him that allows you to make such a claim with persuasive confidence.
With regards to his consistency and mental tenacity, how would you feel as a player being forcibly relocated to a team towards which you felt no loyalty? I think it's undebatable that your production would suffer visibly. Obviously there have been articles repremanding his motivation, but you need to consider what he's been through, with the AHL drama, military fiasco and his forcible relocation.
From everything I've seen, he is probably the best caps forward right now. He is physical for a guy his size, backchecks with the best of them, and creates chances for himself and his teamates when he is on the ice. He has, literally, one of the best wristers I've ever seen, and will take a shot from everywhere.
He's obviously no Malkin, but thus far has proved more at the NHL level. Malkin is also playing on a line with Crosby, which will help him produce--by saying that I'm not trying to detract from his obvious talent (even though everyone will twist my words in order to think that I am), but when you compare Malkin's linemates with Semin's, there's a clear disparity. Yes, Semin doesn't draw the oppositions top dmen, but I think playing with Crosby adds more to Malkin's production than playing with the 2nd pair adds to Semin's production.
I honestly don't think Malkin's point potential exceeds Semin's that much. He will probably produce more points overall, but Semin has 50 goal potential, something Malkin might hit once or twice but not on a regular basis.
Malkin's potential I see as 40-65-105
Semin's potential I see as 50-40-90