She was "Miss Congeniality," a popular, well-paid Hollywood actress. He was a reformed bad boy turned successful businessman and reality TV star.
But the couple seemed to prove naysayers wrong, finding domestic bliss in Los Angeles and Austin, Texas, while raising James' three children from his two previous marriages.
"He's gotten over the wildness and I'm the wild one now!" Bullock was quoted saying in People magazine in 2006.
"Obviously we know Jesse James has a colorful past," E! gossip columnist Marc Malkin told ABCNews.com. "But all things indicated that he was so happily married. He had settled into this nice life as her husband. The guy was crying when she won her Oscar."
"Was he crying for Sandra?" Malkin wondered. "Or was he thinking, 'Oh God, this is going to come out?'"
"This," the world knows by now, is the tabloid report that James had an affair with Michelle "Bombshell" McGee, a San Diego tattoo model who reportedly also worked as a stripper. McGee told In Touch Weekly that she began an 11-month affair with James while Bullock was filming the Oscar-winning "The Blind Side."
Then came the news that Bullock had moved out of the Southern California home she shared with James, less than two weeks after she received the Oscar for best actress. She also bailed on the London premiere of "The Blind Side."
On Thursday, James, who still wore his wedding ring, was photographed walking his three children to school -- without Bullock.
He also released a statement taking responsibility for the couple's heartbreak:
"The vast majority of the allegations reported are untrue and unfounded. Beyond that, I will not dignify these private matters with any further public comment. There is only one person to blame for this whole situation, and that is me. It's because of my poor judgment that I deserve everything bad that is coming my way," James wrote.
He also asksed for forgiveness. "This has caused my wife and kids pain and embarrassment beyond comprehension and I am extremely saddened to have brought this on them," he wrote. "I am truly very sorry for the grief I have caused them. I hope one day they can find it in their hearts to forgive me."
Bullock's rep did not respond to requests for comment.
If the stories are true, this could be a sad ending to an unlikely fairy-tale romance.
"It seems to me that these really successful guys, if they end up with a beautiful sweet woman, go for something opposite," said Malkin, comparing James with Tiger Woods.
The difference with Woods, he said, was that there was no past history with women to compare his alleged affairs to.
"With Jesse, once you hear who the woman is, you think, 'Oh he's up to his old tricks,'" Malkin said.
From Adult Entertainers to America's Sweetheart
McGee, who appears tattooed from head to toe, bears a striking resemblance to James' second wife, tattooed porn star Janine Lindemulder.
Like Lindemulder, McGee works in the adult entertainment industry, as a fetish model and sometime stripper, according to Radar Online. She was raised Amish and told In Touch that she thought James was separated from Bullock or else she never would have had an affair with him.
James' volatile relationship with Lindemulder was recorded on the Discovery network special "Motorcycle Mania 3," but little is known about his first wife, Karla James, whom he met before he became a popular television personality.
James and Karla have two children, daughter Chandler and son Jesse Jr., and Karla reportedly lives within walking distance of James' oceanfront home near Long Beach, Calif.
James, who claims to be a relative of the famous outlaw Jesse James, has made no secret of his past. According to Fortune magazine, he was a regular visitor to California's juvenile detention centers as a youth. His college football career ended early with a knee injury but he found work as a bodyguard, touring with Madonna, Nirvana and Metallica.
Injured on the job, he returned to his first love -- welding -- and, with his longtime interest in motorcycles, opened his own shop, West Coast Choppers, in Long Beach in 1992.
The company grew into a high-end custom bike shop with customers like Keanu Reeves, Shaquille O'Neal and Kid Rock, and caught the attention of the Discovery Channel, which made James into a star with "Monster Garage" in 2002.
James married Lindemulder, who is also known for her association with punk band Blink 182, that same year. Their marriage lasted only a year. According to Lindemulder's attorney, James left her when she was seven months pregnant with their daughter Sunny.
James met Bullock in 2003, when she brought her then-10-year-old godson to the set of "Monster Garage" for a tour. Sparks flew, but James decided to approach this relationship differently. "I took my time and got to know her and did it right, and it was a great courtship," he told People magazine in 2006.
Bullock's Long-Awaited Marriage
Bullock, who was once engaged to actor Tate Donovan and involved with Troy Aikman and Matthew McConaughey, put off marriage, which she once called "a death sentence," and focused on her career, until she married James in July 2005 at the age of 40.
"Everyone was surprised when they got married," Malkin said. "But she put a lot of thought into this. "Her romantic life was never messy, there was nothing to indicate she ever made horrible love choices."
Bullock even put her career on hold while helping to raise James' three children and got involved in his custody battle with Lindemulder over Sunny, whom he successfully fought to keep after Lindemulder went to prison for tax evasion.
"I myself have stopped working like I used to in order to be here with Jesse and the kids because we are on constant high alert," Bullock wrote to the court, "never knowing what condition Janine will be in, and even more concerning, the condition [the girl] will be in."
Now, amid reports of James' infidelity, Bullock's relationship with James and his children appears up in the air. But Malkin thinks Bullock will be fine.
"This is a strong woman," he said. "No matter what happens, she's going to come out strong. This is not someone you push around. As sweet as she is, she's tough."