This will probably be downvoted to oblivion, but I just want an honest explanation.
The way I see things, not only would Stannis make a lackluster king, but he’s not a particularly good guy.
If he did become king, he would lack a strong heir which would make another war far more likely. His new religion puts him at odds with almost all of the lords of Westeros (not to mention the smallfolk). And he has chosen advisers that mean to undermine him or play him (Melisandre, Alester Florent) and rejected good advisers such as Maester Cressen and arguably Davos. He also rejects savvy political deals like an alliance with Robb. Finally, he’s not liked by nearly anyone in Westeros.
He’s a very resentful man. He’s bitter that he wasn’t given Storm’s End. He’s bitter Robert preferred Ned to him as hand after Jon Arryn dies. He’s too stubborn to ask for help, foolishly thinking that he shouldn’t have to ask for support (for example from the Vale) because his claim is so strong.
He thinks its justice to cut Davos’s fingers off. The true punishment for smuggling would be death, or he could spare him entirely, but taking fingers and giving a knightship+lands is a stupid compromise. In any event his morality is inconsistent. In one sense he talks about what is inherently fair or right, but he also decides to burn Edric Storm which is ‘wrong’ but would lead to fewer deaths (based on his belief in magic). And somehow Salladhor Saan doesn’t get punished.
And let’s examine his claim: He’s brother to the usurper of a three century long dynasty. Viserys, Dany, and Jon Snow have a better claim (he knows about at least one of them) and even Renly seems to have been the preferred (trueborn) heir to Robert (at least in Stannis’s mind). I’d also suggest that he doesn’t have enough evidence to be 100% sure that Joffrey isn’t legitimate.
People also talk about his prowess as a battle commander. But he doesn’t always have good outcomes. Storm’s End nearly starved out in Roberts Rebellion. He failed to capture Dany and Viserys at Dragonstone. He lost the battle of the Blackwater. And he decides to march to Winterfell in a blizzard. He also seems completely unconcerned with the morale of his troops.
I do have to concede that he does some pretty good things too. Answering Maester Aemon’s call to come to the wall as only one example. I just don’t see how these are enough to overcome his shortcomings as character and make him a fan favorite.
Please enlighten me.