There are many exploits in older games on consoles (Twilight Hack for the Wii and soundhax for the 3DS are the first that come to my mind) that allow arbitrary code to run, which is what enabled people to install software like the Homebrew Channel or custom firmware. However, there are some key differences here. First, each of these exploits has been for the benefit of the user. They usually are a first step towards modifying the console in question to be able to run unlicensed software and/or backups of games. Second, they tend to rely less on in-game items and more on hacked save files that are modified to put code in just the right places to be executed upon loading the save, or soon thereafter. And of course, none of these can be considered viruses, or even malware really.