I am definitely unhappy with all of the candidates.
On the Republican side, every candidate except for maybe Trump (I have no clue what he actually believes) and Christie would not just be a bad president but would instead be a horrible president. All of them have tax plans that make no actual sense even mathematically. Most of them are extremist hawks. They all want to destroy unions and impose ridiculous restrictions on abortions (as well as defund Planned Parenthood based on videos that have been proven to be fake). While I still probably wouldn't vote for a moderate, it would be nice to have someone who isn't insane running.
Hillary is probably the worst center-left candidate that the Democrats could have chosen. I don't trust her to actually continue to fight for progressive causes if she is elected and the only way that she could get anything through Congress is by making disadvantageous compromises with Republicans in the House. To make matters worse, she won't even admit that she couldn't get stuff passed while the Republicans control the House. She literally has said that she considers Republicans her enemies and that she wants to expand Obama's legacy, but she expects Republicans to work with her better than they do with Obama. All that we'd get from her is another 4 years of gridlock with nothing getting accomplished until the voters get sick of it and go with a Republican over her in 2020.
Bernie is a great person who I have a lot of respect for and agree with on most of his ideas, but he is an extremely flawed candidate. He has little foreign policy expertise, and while that isn't a massive problem, he is doing no work to actually correct it. Many of his proposals are broad ideas that he hasn't worked out the specifics on yet. Against a half-decent group of Republican candidates, he would easily lose in the general election (luckily for him the current options for Republican nominee are horrible). He isn't willing to actually be aggressive and press Hillary on flip-flops, her inability to get anything through Congress (at least he has is idea of a political revolution), and stuff like her accusations of sexism. In addition, his campaign seems poorly run (for example, his decision to hold rallies in Minnesota a few days before Iowa makes little sense). I love his positions and I think he is a great person, but he is not particularly good at representing his positions.