Generators, I've found, tend to produce bland characters. There are few, if any, substitutes for spending time with your characters. Obviously you can't meet your characters in-person. What you can do is use writing prompts to put characters in everyday situations and see how they handle themselves.
A useful tool is stereotyping your character. Think about all your favorite characters, or the characters you want to imitate. Now draw up a character diamond of this stereotype.
A character diamond is a collection of four traits that best describe a character. Usually one of the traits is negative, called The Flaw, and the other is positive, called The Highlight. People change in bad or stressful situations, and their true nature, which is normally hidden, tends to come out. The trait that emerges during a conflict is called The Shadow.
How a character acts in everyday life is called The Facade
The Facade is the top of the diamond, The Flaw is on the left, The Highlight is on the right, and the Shadow is on the bottom.
To be clear, a character diamond only lists the most dominant of traits, and is just a tool getting a better grasp on who your character really is.
Now, think, how is my character different? How can I distinguish them from the stereotype? Often, being unique is not a requirement to hold readers attention; an interesting character can be made by a couple degrees of difference. Change either a character's Flaw or Highlight, and either The Shadow or The Facade to some other trait to create an interesting new persona.
To help you along, you should take a look at TV Tropes which, despite the name, has many articles, and discussions on characters from novels, as well as stereotypes, and gives more specific examples than I could possibly ever list. Also Google "character diamonds" for articles that go into greater depth. Getting a list of character traits is also useful for gaining some ideas.
Blindly asking questions without knowing who, even in the simplest sense, your character is on the personality level, is a recipe for boring. Answering some basic questions about the character is good, so long as you ask the right questions.
Too many forms provide a laundry list of physical questions, hair, eyes, height, build, clothing, gender, age, occupation, etc. The problem with this is beginning writers assume that these questions are important; are these questions important, really? The answer to that is only if the answers help tie the character to the narrative, or inspire further development.
It is the difference between John Doe, thinning hair, who works as a chemistry teacher in some boring this is my life sort of story, and Walter White, worried about his thinning hair and thinning health, dying of cancer, and using his occupational knowledge in chemistry to cook meth so his family won't suffer financially when he is gone.
Spend some time with your characters, their (supposed) to be people too! You want your readers to perceive them as real, right? After all, characters are how your readers connect to the narrative. When a character feels like a person, it engages the reader's suspension of disbelief, so to me characters are the most important part of writing. Don't do your characters, the people of your mind, injustice by asking the wrong questions, and writing them into a narrative before really knowing who they are.