God of War 3 doesn't effect all the gamers who were exclusive to the 360. I understand that an overhyped game like God of War 3 might turn some heads, but this game didn't get the sales it deserved on either console. According to VGChartz, the PS3 version sold more in all regions.
As for Darksiders, the game isn't even comparable God of War 3. The game doesn't even hold a candle to Dante's Inferno. How the game is getting sequel surprises the hell out of me. Good thing you brought it up, because both versions of Darksiders happened to sell more than either version of Dante's Inferno, and I didn't even know about the game until the demo appeared on the PSN. So if it had an advertising budget, then it wasn't very big at all.
As for Dungeon Siege 3. It received a score of 72 and is a Diablo clone. Sacred 2 received 71, Sacred 74, Untold Legends 1 and 2 65 and 68, Champions of Norrath 85, Baldur's Gate Dark Alliance 87, Dark Alliance 2 77, and Return to Arms 77. Aside from Champion's of Norrath and Dark Alliance, and obviously the Diablo series, these games just don't get high ratings, no matter how good they are.
The only thing about Dungeon Siege 3, like these other titles, is that it's not a super high profile game. I can only go by the demo of Dungeon Siege 3, but it was an enjoyable game. It's something that if I went out and purchased it right now for $39.99, I wouldn't feel like I wiped my ass with the money and flushed it down the toilet which is exactly how I'd feel if I were to go and repurchase Final Fantasy 13 again.
I only mentioned Dante's Inferno and Dungeon Siege 3 because advertising for these two games were pushed more than any game this gen in my opinion.
Also, reviews don't really factor in as much as you'd think. Because a game that got decent advertising and good review scores is Brutal Legend. This game sucks balls in my opinion, yet the scores it received on Metacritic is 82(higher than most of those good Diablo clones I listed.) However. This game sold like crap. What? Decent advertising and a high Metacritic score and the game bombs? I thought Metacritic was like the bro code. Everyone on the internet lives by it.
*edit*
I think regardless of advertising, people pick and choose their favored games at random. One of my best friends favorite games are UT3 and Call of Duty, but dislikes games I've recommended him such as Borderlands, Battlefield Bad Company 2, Mirror's Edge, Uncharted 2, etc, etc. He dislikes Yakuza 3, but he likes garbage like Castle Crashers. He likes Champions of Norrath, Return to Arms, and the Untold Legend games, as do I, but he dislikes Sacred 2(which I happen to like more than the others.) It's like. Seriously. What the fuck. Do people just pick this shit out of a hat. Like I said he's one of my best friends, but when we hang out we rarely game together because he has such shitty tastes.