While their weekly numbers must be taken with a grain of salt, they're pretty much the only place to get sales data on older titles (under "world" then "software", you can get data on volume shipped if it passes a million).
Since they also list total console sales, it's easy to figure out what kind of attachment rates (ie, how many GBA owners bought Ruby/Sapphire, then figure out a %) for franchises, which tend to be somewhat consistent.
Also, regarding your Halo comments, keep in mind that this site is tracking worldwide sales. A series like Halo, while extremely popular in America, is nonexistent in Japan...a place where this game has already sold over 5 million copies.
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While their weekly numbers must be taken with a grain of salt, they're pretty much the only place to get sales data on older titles (under "world" then "software", you can get data on volume shipped if it passes a million).
Since they also list total console sales, it's easy to figure out what kind of attachment rates (ie, how many GBA owners bought Ruby/Sapphire, then figure out a %) for franchises, which tend to be somewhat consistent.
Also, regarding your Halo comments, keep in mind that this site is tracking worldwide sales. A series like Halo, while extremely popular in America, is nonexistent in Japan...a place where this game has already sold over 5 million copies.