The Nintendo 3DS might have had a slow start, but thanks to a major price break that occurred so close to launch, the eShop, and Monster Hunter 3G, it's topping the charts. In fact, it broke Japan's sales records for selling 5 million consoles in 52 weeks.
The Nintedo DS previously held that record with reaching 5 million units sold in 56 weeks, and the GameBoy Advance once held the record at 58 weeks.
Note that this is actual sales, and not units shipped. It just goes to show you that great things can happen when you lower the price to under $200 (around 16,000¥). Nudge, nudge, wink, wink, SONY.