Haaland has 26 goals - 11 more than Lewandowski. And if we compare City's balance of power against all other teams in the league and the same balance of power between Barcelona and all other teams, then I would say that Haaland's goals are more valuable. Even Benzema, who missed a lot of games, is only 4 goals less. In general, I think that Lewandowski performs at a high level, but not such a top one to somehow pay attention to it.
I have different opinion about Lewandowski, Benzema has less goals and yes it is mainly due to him missing so many games, but first of all missing so many games is bad for your club, which means he wasn't much of help during those games whereas Lewandowski played as many as he could.
However, Lewandowski is playing for Barcelona for the first time, it hasn't even been a year, Benzema has been there for god knows how long, of course he would play better if given chance, because he has been there for so long. Haaland on the other hand is another story, that guy is just insane, he is the greatest scorer I have ever seen and I have watched Ronaldo and Messi all my life.