You get this feeling though that someday the videogame industry is going to be like film and music industries where there's this handful of a big players and no one else.
Well, there's plenty of else and it's not that hard to enter the market. What keeps the music and film industry oligarchy so strong is that they control the primary "distribution" channels, TV and radio. Videogames are still primarily sold in stores where anyone can get something on the shelves without a real way to bribe them into an exclusive agreement (retailers tend to be larger than videogame companies while radio stations are smaller than music labels). Games also use the internet which, unlike TV and radio, don't use a controlled spectrum and anyone can add a website to the 'net while only a handful can set up a TV or radio station.
Also big companies are only really needed for blockbuster titles which Nintendo hurt badly with their disruption. If Sony and MS had dominated, sure, you'd see small players having little chance of competing but with the market being disrupted and allowing cheap games to beat out expensive "AAA" titles there's opportunities for new players again.
This is also how disruption kills the "videogame industry": The companies that refuse to adapt to the "crummy market of non-consumers" sit in a shrinking market, their profits go down while the costs go up, they need more strength to make another sustaining development and in order to keep making AAA games they merge together, then that game fails to make the money back and layoffs follow, shrinking the company and in the end it's as if one of the former companies had died.
THIS is the videogaming Nintendo is killing!