The Lumia 800 and the N9 currently have the worst cameras that Nokia sells.
Judging by resolution charts, the 4S beats them cleanly. The E7, X7, E6 and such EDoF cameras even seem to perform better.
The N8 makes the 4S camera look like a toy though.
Nokia 2600 (2004) -> Samsung i780 (2007) -> Nokia 5800 (2008) -> Nokia N8 (2010) -> Nokia C7 (2011) -> Nokia E7 (2011) -> Nokia X7 (2011) -> Nokia E6 (2011) -> Nokia N9 + Asus TF101 (2011) -> Nokia Lumia 800 + Asus TF201 (2012) -> Nokia 808 + Blackberry Playbook (2012) -> Blackberry Q10 (2013) -> Sony Xperia Z2 Phone + Tablet
Dev blog: http://www.qtness.com/blog/