They should work on exclusives for each platform as those tend to have very good sales (MW2 was an anomally and not the norm). For example if they would have focused their resources on Dante's Inferno to either be a 360 OR a PS3 exclusive, the end result would look more favorable. In the demo, outside the CG's, the rest of the game looked mediocre and felt like GOW's retarded brother, although the holy and unholy specs look somewhat interesting. Demon's Souls is a good example, although they are at nearly half a million, it was a game that was made on a low budget, and keep in mind it wasn't released in Others. Also it was a niche title. I am pretty sure a DI that would have taken full advantage of the 360, would have had potential of high sales.
Note, I am a PS3 owner and fan, but I am aware of the 360's selling power with exclusives. DI sales would most likely be overshadowed by GOW3 on the PS3 side, thanks to DI being labled as a GOW clone.
Make games, not war (that goes for ridiculous fanboys)
I may be the next Maelstorm or not, you be the judge http://videogamesgrow.blogspot.com/ hopefully I can be more of an asset than a fanboy to VGC hehe.