http://www.m-create.com/ranking/
Media-Create does not combine the Pokemon games, which is why Animal Crossing is only the second DS game to surpass that milestone in Media-Create numbers. New Super Mario Bros. passed 5 million about 19 months from launch, and Animal Crossing has been on sale for 38 months. Based on Famitsu data since 1996 and shipped numbers from prior to that via Captain Smoker, these two are the first non-bundled, non-combined SKU games to cross the 5 million mark in Japan ever.
Edit:
February 8: Animal Crossing: Wild Word crosses 5 million in Dengeki.
June 7: Animal Crossing: Wild World crosses 5 million in Famitsu.
Media-Create said:『おいでよ どうぶつの森』が累計販売本数500万本を突破
旧作市場においては、『おいでよ どうぶつの森』が累計販売本数で500万本を突破した。DSソフトとしては『New スーパーマリオブラザーズ』に次いで2タイトル目の快挙となる。発売から3年以上経った現在でも1万本近く販売しており、定番として息の長いセールスが続いている。
Google-donny2112 translated said:Animal Crossing: Wild World Exceeds 5 Million in Total Sales
A long-time presence in the market, Animal Crossing: Wild World has surpassed 5 million in total sales. In DS software, it follows New Super Mario Bros. as the second title to reach this achievement. Despite being on sale for more than 3 years, even now it is selling almost 10,000 weekly, and its longtime sales look to continue.
Media-Create does not combine the Pokemon games, which is why Animal Crossing is only the second DS game to surpass that milestone in Media-Create numbers. New Super Mario Bros. passed 5 million about 19 months from launch, and Animal Crossing has been on sale for 38 months. Based on Famitsu data since 1996 and shipped numbers from prior to that via Captain Smoker, these two are the first non-bundled, non-combined SKU games to cross the 5 million mark in Japan ever.

Edit:
February 8: Animal Crossing: Wild Word crosses 5 million in Dengeki.
June 7: Animal Crossing: Wild World crosses 5 million in Famitsu.