I read somewhere that Nintendo sells as much software as the next top 4 publishers combined! Vgchartz' numbers seem to support the claim.
How can this be, Nintendo has been making the same type of games since the NES days you say?
That's exactly the reason why Nintendo is so dominant software wise (aside from making quality software). Over the past 15 years or so developers have been shifting more towards the male power I'm-a-bad-ass type games with a darker and more serious tone. Those type of games have a very limited appeal to the broader market.
What about the gamers that just want to have fun and don't take gaming so seriously? What about the gamer that likes lightheartedness and not keen on realistic violence? Nintendo's game catalog provides gamers with such elements and since Nintendo has less competition in that area it is much easier to be successful. And hence that is why the Wii and DS are so successful.
New Super Mario Bros. Wii has already sold 10 million and mostly likely reach at least 20 million. Yes it is pretty much the same Mario Bros. game you played when you were a youngster with added multiplayer, but there are hardly any other games like this in the market that are simple yet really fun and thus it sales like candy. The super hardcore gamer may have grown out of Mario Bros. but what about the next generation?
Kids make up a large part of the gaming market. Do publishers expect them to play Call of Duty or Left 4 Dead with complex controls, realistic violence and mature themes? When they do come out with kid friendly or broad market friendly games they are typically shovelware made by their third rate developer teams. They are leaving a lot of money on the table with their focus.
If developers or publishers were as half as smart they should take some notes from Nintendo.
Just my two cents.