By far the naughtiest were the Germans, with 43 per cent of them admitting playing the field, far behind the Italians and the French at 34 per cent and 32 per cent respectively. ::)
http://www.telegraph.co.uk/news/worldnews/europe/france/10665283/Britons-most-faithful-partners-in-Europe.html
That quote above was for the German woman. Germany must be a fairly egalitarian country, the gender's cheating rates are the closest. :P