For cartridge roms and pressed CDs the failure rate is much, much lower than the console and the expected life span much longer. Not to mention it's often possible to back those mediums up and play the backups or original media on another console.
For carts this is (mostly[1]) true but honestly I'd be pretty surprised if the average CD outlasts a console that used mostly flash to store the games on. Sure if the flash has had consistent write cycles for years it might fail eventually but probably people will be finding games intact on wiis for a long time yet.
A lot of video game CDs barely lasted the life of their console without becoming basically useless.
[1] There are mask roms that are prone to failure, and some NES for eg. games are vulnerable to progressive failure of their battery backed RAM chips, which were not just for save backup but were also often used as extra RAM with a lot of write cycles (and to be clear, I don't mean the battery dying - I mean stuck or flipped bits on the ram itself).
