UK:
* Alexandra Burke (2008): Her powerful rendition of "Hallelujah" left the judges speechless and propelled her to win the competition.
* Olly Murs (2009): He brought infectious energy and charisma to his performance of "Crazy Little Thing Called Love" and went on to become a successful pop star.
* James Arthur (2012): His soulful voice and emotional rendition of "Impossible" resonated with audiences and secured him the victory.
* Ella Henderson (2012): Her unique voice and powerful performance of "I Know You're Gonna Love Me" made her a fan favorite and she became a successful artist.
* Fleur East (2014): Her energetic and entertaining performance of "Uptown Funk" became a viral sensation and led to a successful music career.
US:
* Melanie Amaro (2011): Her soulful voice and emotional delivery of "No One" captivated the judges and audiences, leading to her winning the first season.
* Fifth Harmony (2012): This girl group surprised the judges with their impressive harmonies and stage presence, becoming a pop sensation.
* Alex & Sierra (2013): This duo brought an intimate and charming performance of "The A Team" that resonated with audiences and led to them winning the competition.
* James "The Voice" Smith (2013): His unique voice and powerful performance of "I Believe I Can Fly" made him a fan favorite and led to a successful music career.
* Rachel Platten (2011): While she didn't win, her audition performance of "Fight Song" went viral and became a popular anthem.
Other notable auditions:
* Leona Lewis (2006, UK): Her rendition of "A Moment Like This" launched her into superstardom.
* One Direction (2010, UK): Though they initially auditioned as solo acts, the judges combined them into a boy band that became a global phenomenon.
* Kelly Clarkson (2002, American Idol): While "American Idol" is a different competition, her audition is often cited as one of the greatest talent show auditions ever.
Ultimately, the best X Factor auditions are the ones that resonate with viewers and leave a lasting impression. This can be due to powerful vocals, unique talent, captivating stage presence, or a combination of all these factors.