It's hard to imagine now, but if you can remember back to 2004, you'll remember that Nintendo were a joke. Dead last in the console market, a boy struggling to compete in a man's market. My, how things have changed.
Following the release of first the DS, and then the Wii, Nintendo are clearly the market leaders in both the handheld and home console markets. It's something we just accept these days, as though it's always been the case, but one look at these hardware sales graphs (courtesy of Nintendo) recording the last 5 years show exactly when Nintendo seized power.
Look at 2006-2008. It's like a retail blitzkrieg.