Checking the three big European Amazon websites (UK, France, Germany), what's more interesting than their discounts for SMB Wonder and Spider-Man 2 are their sales figures over the past month on each respective site.
In the UK Spider-Man 2 did the best across the three countries with 10k+ copies sold. In France it's only 5k+, in Germany 7k+.
SMB Wonder doesn't even have a sales figure on Amazon UK, so it's probably safe to assume that it's below 5k; in any case, this lines up with the overall UK sales charts for physical games where SMB Wonder did less than SM2. In France SMB Wonder stands at 20k+, in Germany even at 40k+.
I do not think that we can extrapolate sales ratios from Amazon, but it's at least very probable that SMB Wonder did beat SM2 in France and Germany. I also doubt that SMB Wonder sold twice as well in Germany as it did in France, because I put that difference down to nothing more than different purchasing habits, meaning Germans are by default more likely to buy video games from Amazon.
Legend11 correctly predicted that GTA IV will outsell Super Smash Bros. Brawl. I was wrong.