I think Kitler nailed the spot here, as well as did NikkoM.

Sega really did prove that it does what Nintendon't by exiting the hardware business, but the kind of advertising doesn't work in the current generation context, if at all these days.
Basically the Segas ads back then were all targeted to kids who needed something to make them feel being "better". Currently, the market is twice as big as it was back then and the kids market is dominated by PS360, when the "attack" ads would have very little impact on Wii as a whole.
Also, the people familiar with "does what Nintendon't" are grown-ups today, and know to call similar advertising as BS, by experience.

But, there is "attacking" marketing; viral marketers basically don't do anything else and the Sony/M$ PR is badmouthing the competition by a large part.

The reason you don't see ads like this against the Wii is that most gamers have grown up. What came off to us as edgy and rebellious when we were young now comes off as immature and a little creepy now that we're older and (mostly) wiser. It always came off that way to the grown-ups, of course, so nothing changes for those who never got into gaming, but attack ads like that would alienate the people who buy games for the main markets.

This leaves an environment mostly free of the childish bickering that marked the Genesis-versus-NES wars (and to a lesser extent the Genesis-versus-SNES wars as well). But since it's really the only thing Nintendo can be attacked on with any semblance of validity, in its absence Nintendo thrives.

Sega's Ad campaign was nothing short of brilliant.  They were taking on Nintendo at near monopoly status and they had to rip and claw market share from Nintendo almost every step of the way.  They went from arcades to a major presence in the home console environment with their Master System/Genesis thanks to those ads.  

Saying that kids dominate the market and wouldn't respond to such ads today is ignorant.  Children imitate their rolemodels and often aspire to be cool and have toys "the big kids" do.   One of the reasons teenage ads are often so powerful is that they appeal not just to teenagers but the generation just below them.

Finally, Sega's exit from the market was not due to poor advertising, it was due to poor decision making and hardware support.  If anything, their powerful advertising methods were one of the factors they prolonged their stay in the market.

@WoW: Ehh... Were you just trying to validate my points or argue against? I think you just wanted to argue for the sake of argument, as usual.

I didn's say Segas ads weren't effective, after all, they were very much targeted at the core audience that time and with the "headstart" Sega had with Megadrive, it really was able to gain ground by being aggressive right from the start. But the biggest reason for Segas success that gen was Sonic.

They do respond to ads like that. But the issue is, that the segment of the market that responds, is already dominated by the instances that are in question in the OP. Basically Nintendo would benefit the most within the segment, if it would start making ads that calls PS360 as systems from history for crippled fat nerds, for example.

Well, Sega exited the hardware market and Nintendo didn't. And i'm not that interested in explaining all my jokes.

Attack ads like those above work on the core gaming market. Considering the core gaming market is already on the 360/PS3 they will have little impact on the Wii.

You cannot simply just say that Sonic is the reason for their success without understand what Sonic is/was.  Sonic was nothing more than a video game character (albeit a very fun game).  It was aggressive marketing and advertising that transformed him into a mascot to be remembered decades later and even rival Mario for a number of years.  The hype, the attitude, and the games all contributed to Sega's and Sonic's image.

Also, your 3rd paragraph is worthless.  Nintendo would not and cannot benefit from attacking its competitors at this point as its target demographics would not be strongly affected.  Older people would not be impressed at all by it nor would the teenage/young adult demographic be phased by it while it's being played along side Gears/Resistance 2 ads.  Sega also played the power and attitude cards, neither of which Nintendo is really in a position to play with its competitors.  Honestly, your only real point would be that Nintendo has the most ground to gain in the teenage/young adult demographic, but it also has very few ways to gain it.

I'm a Mac!

@WoW: Sonic was indeed an aggressive character, in relation to the "friendly" Mario, but it was more like the advertising made to advertise Sonic, instead of Sonic made for the advertisement purposes. When you look at Segas advertising during the Megadrive, it's all about Sonic, whether it's about blast processing or the attitude in general, everything somehow is implying to what Sonic games were in general. Sonic the Hedgehog was propably the most meaningful game that gen (for it being a game that could "pull it off", not because it was marketed).

Nintendo would gain within the demographic, which was the whole point in the sentence, but it surely would lose in general. It also means, that Sony and M$ has very little to gain in the same segment from Nintendo.

Nintendo has turned their image from "for kids" to "for families" and "for everyone."

Attack ads used to work because you just had to attack kids, and say that you're for 13 year old MEN, so all the 12 year old BOYS would feel insecure and really want your product.

But now if you attack Nintendo, it looks like you're attacking families or old people or girls or attacking everyone, and nobody likes that. You can't have a commercial saying old people and girls are dumb and real MEN play real awesome manly Gears of War and God of War.