Euron Greyjoy has long been a (male) fan favorite of the books. At first, it would seem that it's because of his physical prowess, his dynamic presence, and his general "alphaness." However, I'd disagree. khal drogo has all those things and yet he is not a favorite among male readers or watchers. This is because he exists more in a female construction of an ideal alpha man rather than a male contruct of an alpha man that Euron exhibits. Khal drogo has a lot of "reputation" among his people represented by his "pretty long hair." He takes the women he wants without asking, but it's more or less established that all the women are ok with it given his status and achievement. He exists to be a fantasy to a woman of a what they would like a man to be but he has no real feelings thoughts or personality of his own...
Euron however is a badass not just because he kills a lot of people but for deeper reasons than that. for one, he beats the odds, the greyjoys casted him out for losing the war and no one wanted him to come back and be king but he TOOK IT ANYWAY. He represents the dark male psychic trait of DEFIANCE.
Euron also has the spirit of boyhood still going strong in manhood. He sees something he likes and just takes it. He likes things a lot of the time because he knows he's not supposed to have it. And the greyjoys that work for him do so not because he's an oppresive ruler and they fear him but because they appreciate his "maleness" his desire to just have whatever he wants simply because he can. He represents the dark male psychic trait of DESIRE
Finally, Euron has a lot of words and self confidence, but after reading about him or seeing him in action for a while you realize that his big sense of self is the least of his powerful qualities. The man is just tough. He beats people all the down. He's fearless and almost fiendish with the way he goes at people. There's nothing at all in the world that seems to cause him to hesitate. He doesn't ask who will let him, he asks who will stop him. He exhibits the the dark male psychic trait of CONFIDENT ACTION
And all of this is to say that he is representative of the "male comeback" to a GOT world that increasingly represents our own. Earlier, Danerys meets with all female leaders who are her current allies. After all they've been through, it seems women have finally taken over the realm. Old lady Tyrell rules now that her son and granddaughter are dead, the snake snake woman runs things now that the viper and the prince are dead, and yet...Euron wipes all that out in such a basic but effective way...he just starts killing.
I don't believe it's an accident we see Euron slaughtering all female cast members. He kills the sisters one by one. His rapacious looking male soldiers take the mother after she asks just to be killed. It's implied that Euron either killed Theon's sister or is going to offer her up as blood tribute to Cersei. I think on some level its supposed to represent the sort of "male comeback" that America has seen in our most recent election--pissed off males who are all going to join together under one guy who's not afraid to be as outwardly misogynitic as they all are deep down inside...The rise of feminist leadership being shortlived...The return of the patriarchy secretly brought back by women who believe they on some level benefit under this system even if it hurts the gender (Cersei) as was thought with Trump election (53 percent of white women voted for him even after his sexist remarks.)
And I believe that's why despite his horribly psychotic behavior male fans of GOT love Euron Greyjoy...