massive games don't sell consoles on day one. they sell them over time as word of mouth spreads and people try it out for themselves and get hooked.
internet forum nerds aside, people don't make hardware purchases day and date with the release of the game they want to play. they'll buy it whenever it's convenient, which might be weeks to months ahead of the release (meaing: they'll find another excuse to get it), or weeks to months after.
to make an immediate hardware boost, you need a price drop. to make a long term hardware boost, you need momentum from games. wii sports is a momentum builder. it got into homes, people tried it, and the wii took off. but if wii sports came out of nowhere tomorrow, you wouldn't see millions lining to buy a wii to play it, because they wouldn't know what it was.
people knew what gta iv was, and they've been buying 360s and ps3s in anticipation of it since day one. and they'll be buying 360s and ps3s to play it for months to come. just not all day one, week one, month one.
it sure was nice of microsoft and sony to not introduce any skus, bundles, or price drops leading up to gta iv. i imagine september 07 would have been much different without a price drop in august and a new limited edition sku. even with those, the boost was mocked by wii and ps3 fans alike.
well, the wii fans are still laughing, i guess.