I voted for Mufasa and Simba, but I will almost say that Mufasa was a better father than Simba.
Mufasa, before he died, was a very wise lion and a rightful king who protected his son Simba the best. Mufasa teached Simba the steps to rule a kingdom, and also teached him which were good or bad things. Also, in the stampede scene, he lefted his life by saving Simba's; if Mufasa didn't save him, Simba probably will be dead in that scene.
Simba was a good father too, but he was over-protective with his daugther Kiara. Maybe because he didn't want Kiara were in problems like him as a cub, or as some fans say, maybe because of the "death" of his son Kopa. (Yeah, I've put "death" 'cause I think he didn't die) Also, Simba didn't trust Kiara when she said that Kovu loved her for what she is. If I were Simba, I'll gave Kovu an opportunity instead don't trust my own daugther. (But I understand that Simba only wanted to protect Kiara because he knew that Kovu was choosen by Scar)