Stannis is waay too tightly wound to be a decent ruler (would love to be his dentist, I'd be set for life). A calculating strategist, capable of commanding discipline but not a man of the people at all. On the "hereditary claim" score, his case is no more compelling than Dany's- and as the series has repeatedly demonstrated, rules of succession only apply when there aren't enough swords around to say otherwise.
Dany has listened to counsel yet made her own decisions, raised an army, established a realm of sorts and at least demonstrated concern for her people. Although the least "raised among leaders" of the three potential candidates (Viserys and Drogo were hardly role models), she demonstrates the most aptitude for rule and capacity to achieve it; first Queen of the Iron Throne for mine. No doubt Cersei would be pleased for her ;-)
Edited by Jeff_God_Of_Biscuits, 30 January 2012 - 12:24 AM.