There isn't much between them and XB1 should lead the holidays

Whatever!Αs you consider that difference small,what else can I say?:P

I'm quite surprised that Driveclub sales in Germany is higher than FH2 by a 1.5:1 ratio.

You shouldn't.:PI had predicted it!hoho!

Notice that percentage? Smash launch week. XB1 was ahead the week before. Should be back ahead next week or the week after.

Not a surprise. Apart from UK where competition is alive between PS4 and X1, in all other European territories is Playstation dominance. Japan and rest of the World the same.

Have to disagree with you there, look at this graph that has been posted earlier:

The Wii U overtook the X1 in week 47 (the week before Smash) and has since stayed ahead in germany.

Are those sales or "search interest"? If sales, what caused the PS4 drop and flatline right before Christmas?

Just to be fair, Idealo.de, the source of those graphs, is a price tracking site. So this shouldn't be real sales data.
On the other hand, it seems to pretty much fit to sales.
And no, the One might need really long to surpass Wii U. No one over here except Xbox fans is interested in it right now.

It's demand. I wouldn't necessarily say that PS4 sales dropped all that much,  could just be that the Wii U had a larger growth percentagewise than the other two going into december, people do say that Nintendo always does exceptionally well during the holidays after all.

Also the whole thing isn't in true proportion anyway.

If it were then the PS4 graph would drop by as much as the Wii U graph rises in the last week, since the X1s share seems to be static at 13% over the 2 weeks.