Sarah Jessica Parker on Sexiness and Success

Sarah Jessica Parker has been a successful actress since childhood, when she starred in "Annie" on Broadway, but it wasn't until her iconic role as a single woman desperately seeking Mr. Right in the hugely successful HBO series "Sex and the City" that she became a certified celebrity.

In her soon-to-be-released film, "Failure to Launch," Parker is again playing a woman who falls for a reluctant bachelor, played by Matthew McConaughey.

In real life, Parker lives a much more stable romantic life. She has been married to actor Matthew Broderick for nine years, and they have a 3-year-old son, James.

The show was so popular it even spawned a "Sex and the City" bus tour that takes fans by Carrie's apartment and some of the New York hot spots featured in the show.

"I'll tell you something, we wrapped the show two years ago, Feb. 4. ... The last line that I ever uttered, working as an employee on "Sex and the City" was 'And you can drive up and down this street as much as you want, because I don't live here anymore,'" Parker tells Barbara Walters in an exclusive interview with "20/20."

Walters spoke with Parker at one of her favorite West Village haunts, and asked what it was like to work with McConaughey, whom People magazine named the sexiest man alive.

McConaughey is sexy, Parker admits, but she tells Walters she prefers her own Matthew's sexiness.

"Sexy is a very subjective thing. And I appreciate and can completely understand why he has been appointed this, you know, or given this title. However, my husband, Matthew Broderick, has qualities that are, to me, really incredibly sexy. ... You really can't compete with him. You know, just his sense of humor or ... his dry-as-a-bone wit or his peculiar perspective on the world or his cynicism, frankly," she says.

Unlike her characters, Parker is happily and comfortably settled into marriage and motherhood. "I'm not saying it's a perfect marriage. And I'm not saying that we don't disagree about things or that I don't annoy him constantly, as I'm certain I do. And that he doesn't, you know? And that there aren't endless issues that enter into things, like, the toilet seat, or picking up his laundry. But for the most part, we seem to have, I don't know, we seemed to have figured it out," she tells Walters.

On Alternate Endings and Success Beyond Her Wildest Dreams

Although the Broderick family has financial as well as emotional security, there was a time in her childhood when her parents struggled to support their eight children, and Parker and her siblings had to survive on emotional security alone.

"There was an occasion where there wasn't Christmas," Parker says. That was difficult, she says, "because what happens after the holiday break is everybody comes back to school and talks about what they got."

As a parent herself, Parker says she now reflects on how difficult it must've been for her parents. "I really think ... how hard that must've been for my parents ... the feeling of failing as parents. ... I think you learn more about your parents at a certain age than you do about yourself," she tells Walters.

While she'd like her son to have siblings, Parker isn't sure she'd like to have such a full house. "I think that we will be thrilled with whatever we are blessed enough to have. I think it's probably very good for him to have a sibling. But we'll see," she says.

In the series finale of "Sex and the City," Carrie reunited with longtime on-again-off-again love Mr. Big to give the relationship "the real college try." But, as the show's executive producer, Parker had considered a few alternative endings.

These were the other options Parker says she considered for Carrie:

She came home from Paris with Alexander Petrovsky, played by Mikhail Baryshnikov, and was going to marry him.

Or, she was going to come home alone from Paris, and just pursue her life in New York, and find contentment among her friendships, without any romantic entanglements.

A lot of people wanted Carrie to come back and be the independent single woman and not commit herself to a man. Parker says she decided against that because "it was a chance for her to be in that relationship on her terms, for the first time in seven years."

Parker tells Walters there are no plans for a "Sex and the City" reunion or a film.

"The end is the end. The sets are gone ... destroyed. Carrie's apartment's been sold," she says.

For a woman who came from such humble beginnings, Parker admits she's achieved a level of success beyond her wildest dreams. "I didn't know this life existed. I mean, I would not have dared to dream this," she says.

When asked where she is in her life, Parker tells Walters, "I am the definition of contentment. That's exactly where I am."