GPUs are definitely a step ahead of the CPUs, and they need to be given the kind of display resolutions in play on mobile devices. So, here we have a comprehensive benchmark of the mobile GPUs against desktop GPUs from 2004-2007:
Given that most of the ARM based CPU competitors tend to be a bit slower than Atom, you could estimate that any of the current crop of smartphones delivers CPU performance somewhere in the range of a notebook from 2003 – 2005. Not bad. But what about graphics performance?
At the end of the day I’d say it’s safe to assume the current crop of high-end ultra mobile devices can deliver GPU performance similar to that of mid to high-end GPUs from 2006.
AnandTech | The Great Equalizer 3: How Fast is Your Smartphone/Tablet in PC GPU Terms.