Where did she go wrong? I'd say she was doomed from the day she decided she wanted to be a pop star. Before the 1999 release of her debut album On the 6 in 1999 when she was 29 going on 30, Lopez was coming off career-best reviews for her performance opposite George Clooney in Out of Sight, an acclaimed 1998 Steven Soderbergh-directed caper that earned only $37.5 million at the North American box office, making it slightly bigger than her 1997 breakthrough Selena ($35 million), though certainly no Anaconda ($66 million in '97) and not even Enough ($40 million in 2002).
I can understand why she wanted to add "pop star" to her name. She was working with A-list directors (Soderbergh) and costars (Clooney), but why should Britney Spears have all the fun on the Billboard charts? With a hit album, perhaps people would even go to see her movies. Her gambit initially seemed to pay off: Her first post-album film, 2000's The Cell, earned $61 million in North America well before her costar Vince Vaughn became the bankable one. It's hard to imagine that people didn't go to see it just because the girl who sang "If You Had My Love" and "Waiting for Tonight" was in it.
Lopez's music career epitomized the catch-22. She wouldn't be as wildly popular as she still is today without it, nor would she be an American Idol judge (a post to which she'll return for the show's 13th season on January 15, after sitting out the Mariah Carey vs. Nicki Minaj session). But while pop success made her a household name at the turn of the century and built interest in her acting projects, I believe it also had a negative effect on her Hollywood career, raising commercial expectations for her films to possibly unreasonable proportions while wildly overexposing her.
Cinderella stories in which the working-class girl meets the man of her dreams (2001's The Wedding Planner and Maid in Manhattan and 2005's Monster-in-Law) brought Lopez her biggest film success and cemented her prevailing onscreen persona: shades of While You Were Sleeping-era Sandra Bullock and early Julia Roberts, complete with the wife-of-an-abusive-monster-fights-back role in 2002's Enough, in which she was Julia Roberts's Sleeping with the Enemy heroine without the great hair or the blockbuster box-office. (It peaked at $40 million.)
For a while, Lopez became a fairly bankable box-office star, scoring as many hits (the biggest of which, Maid in Manhattan, grossed $94 million) as misses. But for all of her Hollywood clout, and unlike every other romantic-comedy/drama fixture mentioned in this post (and some who are not, like The Family Stone costars Sarah Jessica Parker and Rachel McAdams), she never enjoyed a $100 million hit in any genre and still hasn't (unless you count 2012's $161 million-grossing Ice Age: Continental Drift, in which only her Bronx accent appeared).
Lopez didn't make their job hard, going through a string of also-famous steadies: Sean "Puffy" Combs (before he became "P. Diddy" and then, simply, "Diddy"), Ben Affeck and Marc Anthony, who would eventually become her third husband, from 2004 to 2012. During the early to mid '00s, following her love life was as popular a leisure pursuit among fans as going to her movies. She was the Kim Kardashian of the day, only everyone knew exactly why she was famous, even if she hadn't done anything particularly impressive to get that way.
But her ostentatious public displays of extreme wealth and her game of musical chairs with boyfriends, fiances and husbands made it hard to buy her as the girl next door that the movie studios were paying her to be. When she tried to sell herself as one in her songs (most notably, two of her biggest hits, 2001's "Love Don't Cost a Thing" and 2002's "Jenny from the Block"), she came across like a businesswoman attempting to convince us that she'd rather be a housewife while wearing a power suit.
America's sweetheart was supposed to be one of us. Julia Roberts and Sandra Bullock were able to convince the public that they were everywomen offscreen even while earning upwards of $20 million a movie. Lopez, dripping jewels and fabulousness, was forever saddled with the "diva" tag. How was America going to call her "sweetheart," if most Americans couldn't relate to her?
She was less Cinderella than Erica Kane, or Elizabeth Taylor, who wisely never tried to be America's sweetheart, leaving that to Doris Day. When Lopez married her Larry Fortensky (Cris Judd), she quickly upgraded him for Ben Affleck, her financial equal, damaging her rooting factor on and offscreen. Her motto could have been "Love don't cost a thing, but it don't mean a thing either if it don't come with bling." Ben Affleck, apparently understanding this, gave Lopez a 6.1-carat pink diamond engagement ring as a sign of his devotion. Some girl next door. At least her love life was more entertaining that her movies.
Lopez and Affleck's joint 2003 flop Gigli ($6 million) is often credited with halting her Hollywood rise, but there were a few more film successes to come (2004's Shall We Dance and Monster-in-Law the following year). Like their predecessors, though, none of them became her Pretty Woman, or her Legally Blonde. By the time she said "I do" for the third time, to Marc Anthony, and gave birth to twins Maximillian and Emme in 2008, her Hollywood heyday was over.
It's possible that it would have ended sooner rater than later, even without the mixed messages of her pop stardom. Few performers in the history of Hollywood and recording have been able to manage simultaneous film and music careers. Frank Sinatra was one of them, but he was a far better singer and actor than Lopez. Diana Ross spent several years as a Hollywood star in the '70s, even earning an Oscar nomination for Best Actress (2007's El Cantante was supposed to be Lopez's Lady Sings the Blues and then never really happened), but Ross's iconhood had already been firmly established in the '60s as the head Supreme.
Today, Diana Ross, whose 1980 smash "I'm Coming Out" provides the soundtrack to Sony Entertainment Television's commercial promoting "J. Lo Movie Month," is a living legend. Julia Roberts, Sandra Bullock and Reese Witherspoon are Oscar winners. Two of Lopez's male '00s costars, Vince Vaughn and Matthew McConaughey, would now get top billing over her. And J. Lo? She's still a pop star, though no longer a guaranteed hitmaker. In Hollywood, she's an also-ran romantic-comedy heroine alongside Kate Hudson, Jennifer Garner and Heigl: America's almost-sweetheart. She'd probably kill for that other Jennifer's (Aniston) film career. Even that other other Jennifer (Garner) gets juicy roles in Oscar-caliber projects like Dallas Buyers Club.
Idol, though, might be as good as it gets in front of the camera -- for now. Her first stint as a judge led to resurgent, if short-lived, Billboard success. (After a half-decade of flops, "On the Floor" was a massive 2011 hit, but none of its follow-ups have caught on.) Maybe her second round as an Idol judge will lead to another pop comeback, or -- finally -- a $100 million movie.
If not, who needs America's open arms embracing its latest sweetheart? There's always that reported $17.5 million a season from Idol, the millions from all her behind-the-scenes projects and Casper Smart to keep J. Lo warm at night.