That's pretty much what I said. The PC and console market may be, as you say, pretty far apart, but it doesn't make any sense to completely ignore one when deciding what is or isn't a "killer app". Oblivion may have been a killer app for 360 had it been exclusive, but it's not because it also has a huge fanbase for PC.
In other news, typing "killer app" makes me feel silly, like I'm using leet speak or something. Blergh.