Go here:
http://www.game-sales-charts.com
I find "Weekly Top 10 Grid (Real Arcade)" to be one of the more useful sets of data. You can see what was popular, and for how long. But you have to go to the last couple pages to see the latest data. (Though the data on that particular chart seems to be from around March at the earliest. The other charts seem to have newer data.)
http://www.game-sales-charts.com
I find "Weekly Top 10 Grid (Real Arcade)" to be one of the more useful sets of data. You can see what was popular, and for how long. But you have to go to the last couple pages to see the latest data. (Though the data on that particular chart seems to be from around March at the earliest. The other charts seem to have newer data.)