I think we can all agree that Girls Aloud (and Xenomania) being able to deliver album after album and keep the standard of quality over the years was special!
You could be right but they weren't the only artist recording an album every year, Rihanna is another example...
Music of the Sun (August 2005)
A Girl Like Me (April 2006)
Good Girl Gone Bad (May 2007)
Good Girl Gone Bad Reloaded (June 2008)
Rated R (November 2009)
Loud (November 2010)
The bigger gap is between Good Girl Gone Bad and Rated R, 2 years, although Rated R is not her most successful album... GGGB and Loud were done in 1 year. I agree with
thomas1700 and
TheGoose, it's more about choosing the right songs and paying for them (or being a good spotter and going for something a bit different). Umbrella was a reject, but Rihanna's team and Jay-Z changed some parts of the song and the result couldn't be better...