I just hope that they are able to salvage Stannis character in this season. Not only the shows lack the inner monologue that shows him not buying the whole R'llor crap at all (that's comprensible), but the whole decision of getting to the Northern wall being yet another case of him obeying the Red Witch demolished his character. One of my most disliked changes that the show made.
As for who should sit in the Throne...
Daenerys: Entitled self righteous teenage girl with no ruling skills or whatsoever, yet witht the Westeros equivalent of nuke warheads under her control. Oh, and she's probably going to arrive allied with the Ironborn. Big huge dose of NOPE here.
Cersei: Ahahahaha, oh, wow. This isn't going to happen. She's going to loos the judgement by trial. Frankengregor fighting for her VS Cleagane fighting for the Faith. She will be killed by the Valonqar, indeed. Albeit "executed" would be the appropiate correct term.
Jon Snow: We would all like for Jon Snow to rule as a King. But Azor Azahi reborn? I'm not so sure of that. If Catelin's resurrection is any indication, we might not like his new persona at all.
The mummer's dragon: Well, no reader truthly likes him because he's just a newcomer that we feel no attachment to. But he is indeed the most qualified to occupy the throne, that's for sure. He got the right education, mindset and advisers. So of course Martin will fuck him up for good
Sansa: She's got the North's loyalty, she's learning about politics with the best teacher ever, she controls the most fertile, peaceful region of the Seven Kingdoms. She will either rule as a Queen in the North or she will sit at the Iron Throne sooner or latter. I could even vision an "Ice Queen VS Fire Queen" type of final conflict between Sansa and Daenerys before the white walkers pours from the North.
Stannis: Probably the most decent King of the lot. I am however unsure about how the hell he could rettain the loyalty of his subjects once the "new true kings" show up. Either way, they guy's got "doomed cause" written all over.