Cowell had been the producer and the creative force of many media, most notably Pop Idol and its international offspring. Beginning, particularly, in the 2000s, this has brought him worldwide fame and greatly increased monetary fortune.

Cowell became a judge on the first season of Pop Idol in the year of 2001, and did the same for American Idol in 2002 and his acerbic style of judging was a major reason for these shows becoming popular. This was especially so for American Idol, where in its first season, talk about "that nasty guy Simon" gained the show media attention, more so than the hosts or contestants. Cowell's fame (or infamy) grew, fed by his deliberately insincere signature phrase, "I don't mean to be rude, but …", inevitably followed by an unsparing denigration of the contestant's talents, personality, or even physical appearance. One from 2005 was "You look like the Incredible Hulk's wife." Cowell also appeared on the one-off World Idol program in 2003, where it became clear that each country's version of the Idol had attempted to come up with its own "Simon Cowell", further proving his effectiveness as a villain. In 2003, Cowell placed #33 on Channel 4's list of the all-time 100 Worst Britons perhaps due to some people perceiving him as spiteful and arrogant.

Cowell's S Records signed the top two finishers of the first season of Pop Idol, Will Young and Gareth Gates, both of whom went on to have #1 UK hits.

In June 2003, Cowell sold his half-share in S Records for $42 million to BMG, thus becoming a multi-millionaire.

I Don't Mean to be Rude, But I Am…

In December 2003, Cowell published a book, I Don't Mean to Be Rude, But I Am…. In it, he recounted his childhood, his years working in the music industry, his experiences on Pop Idol and American Idol, and finally, his tips for being successful as a pop star.

Il Divo

Efforts began in 2001 materialised in 2004, when Cowell returned to his group manufacturing roots with his latest brainchild, the internationally successful operatic pop group Il Divo, consisting of four young opera singers of four different nationalities. Inspired by the success of Il Divo, Simon created a child version, Angelis who entered the charts at number 2, beating competition from many similar groups emerging at Christmas 2006.

The X Factor

In 2004, along with Sharon Osbourne and Louis Walsh, Cowell was a judge on the then-new British TV talent show The X Factor, which he created under his production company, Syco. The X Factor was a success with viewers and returned for a second and third series in 2005 and 2006.

Cowell was sued by Pop Idol creator Simon Fuller in 2005 over The X Factor, saying it was too much a copy of Pop Idol, but after a while, they settled out of court. The case was adjourned on the first day, and settled with Cowell's Idol salary increased to $36 million a year from $8 million, while Simon Fuller would gain a minority stake in X Factor. Upon the settlement, Cowell signed a new five-season American Idol agreement with Fox.

American Inventor

On March 16, 2006, Simon Cowell's next competition show, American Inventor, debuted on ABC. Fledgling entrepreneurs from across America will compete to see who can come up with the best new product concept. The winner, Janusz Liberkowski, received $1 million Dollars and the opportunity to develop his idea into a business. The show returns again in 2007.

America's Got Talent

Cowell is the executive producer of America's Got Talent, along with Fremantle producers of the Idol series. However, Cowell is not a producer of any of the Idol series, only a judge. The show was a huge success for NBC, drawing around 12 million viewers a week, and beating So You Think You Can Dance on FOX (produced by rival and Idol creator Simon Fuller). The show heads to Britain and Australia in 2007.

Celebrity Duets

Cowell also executive-produces Celebrity Duets, which can be described as "an Idol show for Hollywood superstars." The show is hosted by Wayne Brady, and its judges are Marie Osmond, Little Richard and David Foster.