I know this is an old post but for some time I've wanted to revisit this topic, so I did some digging. It turns out OECD has a data table (2003. The World Economy: Historical Statistics (Paris: OECD)) that I've seen as a source in a paper from Berkeley and London School of Economics (http://edoc.hu-berlin.de/series/sfb-649-papers/2008-68/PDF/68.pdf). I'm guessing the source is reliable enough for most purposes.
Here is the link: http://www.ggdc.net/maddison/historical_statistics/horizontal-file_03-2007.xls
And for the people too lazy to make their own graph, here is the GDP per capita for the major powers. I left out China because although it was a big country involved in the war, I didn't want their low numbers to mess up the graph.
Germany was indeed poorer than UK before the war but not far behind France.
I find it interesting how WW2 was detrimental to many of the economies on the short run but after a decade or two they all caught up to their trend lines.