Majin-Tenshinhan's post sums up my thoughts on the matter.
Not just with videogames, but with any product. If you really love a particular snack, TV series, music band, brand of clothing, movie, etc. it's to your benefit that said product does well in the market.
If it sells well, it will continue to get support.
In the case of videogames, if a particular IP sells well, you can count on the company that produces it to consider making more games, instituting a series. Other companies may look at the game's good sales and consider creating similar games. In this instance, more games like the one you like (even if they're copycats of the original) is normally a good thing.
In the case of consoles, if the machine you paid hundreds of dollars for is only bought by a small group of people, it will end up with a minuscule userbase. Small userbases pretty much ensure lower game sales, as no title is ever going to be bought by 100% of console owners (unless the game comes packed-in or something). So, if the console has a small userbase and games don't do very well on it, it won't have a significant enough presence in the market for game developers to consider making games for the system. So you'll have a less varied game library available, you'll receive less support for your game machine and in the end you get a lot less bang for your buck.
This sort of information is especially useful for potential customers. If you are weighing your options between two or more game consoles and find out one of them is selling much better than the other(s), you know you have a greater chance of investing your money on a machine that will get better support overall.
So yes, monitoring how consoles and games sell will always be of interest to those of us who love videogames.
Make sure the shadow you chase is not the one you cast.
