I don't understand how Barkov is leading in terms of who had the better career, especially by this wide of a margin. (As of now more than 76% of people said that Barkov had the better career).
The difference in their offensive production is massive. Looking at where they ranked in the scoring race (which we need to do, because Barkov peaked when the league was higher scoring), Getzlaf has four of the five best seasons (2nd, T-6th, T-10th and T-11th, vs 10th for Barkov). From 2008 to 2017 (a full decade), Getzlaf was 8th in scoring and T-8th in PPG (min 300 GP). If I use a shorter period (2008 to 2015), Getzlaf looks even better - 7th in scoring, T-5th in PPG. I can't find any similar timeframe for Barkov.
It's not just about the stats, it's also about how the players were perceived. Getzlaf has 3 of the top 4 seasons between them in terms of where they ranked in Hart voting (2nd, 6th and 7th vs 6th). Barkov never finished higher than 5th in voting for the year-end all-star team (Getzlaf surpassed that three times).
Getzlaf scored a fair bit more per game in the playoffs, and he did this during a lower-scoring era (so on any type of "adjusted" basis, he'd be even further ahead). Both players were the #1 forward on a Stanley Cup winning team. Granted, Barkov had one more trip to the Stanley Cup finals, but Getzlaf had three trips to the conference finals (one as unquestionably his team's best player, and one more as at least arguably his team's best player).
Obviously, Barkov is better defensively. Two Selke trophies (and one more year as runner-up) is significant. But Getzlaf was quite strong defensively, and he got some fringe support for the Selke in a number of seasons. If you look at the so-called advanced stats, Getzlaf actually does better in terms of relative Corsi and Fenwick (5v5, over the span of their careers - which also includes several of Getzlaf's declining years). Their defensive zone starts are similar (both round to 51% at 5v5). Barkov averages 27 seconds more per game on the PK (which amounts to one extra PK shift per game - which is a positive, but it's not a huge difference either).
I don't understand how Barkov has had the better career, when he's played in almost 400 fewer games, has fared much worse in the scoring race and for the Hart trophy, has fewer deep playoff runs, and scores at a significantly worse rate in the postseason. I think you'd have to put an unreasonably high value on the Selke trophy to conclude, today, that Barkov has had the better career. (I agree there's a good chance he'll eventually surpassed Getzlaf though).