music games have it all wrong, and this is why they're fading off the radar. Each game's developer should NOT be responsible for the instrument charting. The artist/studio should be. When we buy a track, we should buy it directly from the artist/studio. The artist/studio would provide us with a particular type of file, which contains the multitrack data as well as the charting. This file would be portable across ALL platforms that support this file type. It would then be the game's responsibility to build the experience around these tracks, providing visuals, story, multiplayer, and game modes however they wish. The gamer would then choose which experience is right for them, and any songs they bought would be immediately available to play on that game.
This relieves pressure on the consumer, who is likely aware that switching games means ditching some songs, and switching games developed by different studios means ditching ALL songs. It also relieves pressure on the game developer, as they no longer have to worry about licensing issues and charting, and can focus more on a polished gameplay.
As it stands now, buying music game songs are equivalent to buying songs over a certain music service, and you can only play the songs on that particular piece of software. Not only that, but if you want to listen to different songs bought somewhere else, you have to open a different program, or perhaps pull out a different MP3 player. Oh yeah, and the song only works on an HP PC, don't even think of playing it on a Dell.
Flame shield engage!