I think there's a genuine lack of strong candidates, primarily on the Republican side but also the Democrats to some extent.
Rubio et al. provide no sense of authority, or driving leadership that I believe is required to win an election, unlike previous presidents.
Scarily Trump may well get the nod, mainly due to his populist stance and mastering the political waffle of saying something yet nothing at all.
He gives people who are disenfranchised the feeling they have a voice. Again don't think he's the man to lead.
From the Democrats, Hillary is a walking talking slogan spouting focus group machine, she has the Clinton and establishment behind her which makes any genuine competition tough.
She says what people want to hear, and will probably pull through due to the woman's, African American and Hispanic vote that her gender and husband brings.
However my favourite candidate and the one who seems to have the most authority and make the most sense is Bernie, he's probably a little old and will struggle to get the nomination due to those supervotes which stand with Clinton as the establishment choice.
He does seem to be getting strong grassroots support though, and would be my choice as next POTUS.