Fifa is arguably the most surprisingly impressive game series sales-wise this generation. Every single iteration has outsold the last, unless I'm reading something wrong.
Fifa 06: 5.11 million
Fifa 07: 6.34 million
Fifa 08: 9.38 million
Fifa 09: 9.34 million
Fifa 10: 10.42 million
Fifa 11: 11.91 million
Fifa 12: 11.98 million (and still sneaking upwards a bit. Should do up to 250,000 more)
And then you have Madden NFL, EA's other major sports series. It's just gone the opposite way instead.
Madden NFL 06: 9.03 million
Madden NFL 07: 10 million
Madden NFL 08: 8.03 million
Madden NFL 09: 7.8 million
Madden NFL 10: 7.42 million
Madden NFL 11: 6.45 million
Madden NFL 12: 5.14 million
It's quite astounding how they managed to more than double the size of Fifa, while halving the size of Madden, all during the same generation. I'm not sure what they did differently between the two, either.