Why they're on the list:
Once upon a time U2 was almost considered edgy. The postpunk energy of early singles like "I Will Follow," combined with Edge's appropriation of Gang of Four's guitar sound and Bono's openly political lyrics made them sound tougher than many of their synth-loving "New Wave" colleagues in the early 1980s.
They quickly learned how to adapt their signature sound for arenas without entirely losing their souls, and then parodied the very notion of selling out with the intentionally overblown Zoo TV tour in the early 1990s. Eventually they settled into a nice, safe career as every world leader's favorite alternative rock band, racking up between 100 and 150 million in sales.
Why they may not be in the games:
U2 talked openly about wanting their own single-artist music game, but that hasn't happened and they still haven't wound up in Rock Band or Guitar Hero. Maybe Bono was too busy splitting birthday cake with Desmond Tutu to make that meeting.