Because unlike Sony and Microsoft, you haven't yet seen Nintendo franchises in HD glory.
On the PS3 side you already saw some serious graphics realism from God of War, Uncharted 2 and the almost real Gran Turismo 5.

On the Xbox side you got Alan Wake with the "best graphics ever" on a console, which seems a reasonable setence, may not be the best but it is a jaw dropping game for sure...

X360 and PS3 already are a couple of systems capable of pulling out very good graphics.
The next Xbox and Playstation, while being obviously more powerfull then its current models, you won't notice as much the difference on the games as you will do on the next Nintendo system,
Which by the way, may be fair to assume that it will easily pull out graphics like this:
http://img11.abload.de/img/2pblu.jpg
http://www.crymod.com/uploads/mediapool/00020hl3.jpg
http://www6.incrysis.com/screenshots/2axca.jpg
(images are too large to fit here, Crysis Real Lifesis mod)
Franchises like Metroid, Mario, Animal Crossing, Pokémon, Fire Emblem, F-Zero, Smash Bros and ultimately The Legend of Zelda are set to impress you in the next iterations with graphics you haven't seen yet on Nintendo games. That will generate the buzz that PS4 and Nextbox games can't, simply because the current games for HD system are already so good looking that the next sequels and new IP's won't have the same "almost realistic" impact as the Wii 2 console and ultimately some may pass unnoticed:
I don't know how the Gran Turismo PS4 game will look, but going more real than Gran Turismo 5 is a huge task. Huge. While doing a Metroid or Zelda more realistic graphics wise than its Wii counterparts will be child play.
"But graphics don't matter that much for the Wii audience" would you argue.
Well, thing is. They do matter =)
Not for the casual crowd which will have plenty of choices with user friendly clean-graphics games from Nintendo, but for the "hardcore" crowd they matter, which will be the ones first noticing how good Nintendo IP's look on the new hardware.
Casual market is assured with some Nintendo blue ocean titles, which will be launched riding the momentum of the current Wii, just like PS1-PS2.
Hardcore Market shall be pleased with the graphics novelty and first time HD epicness of Nintendo stuff.
Owning casual market + hardcore market + riding existing Wii momentum (nintendo won't launch an expensive console like PS3) = 1st Place
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P.S - In the case next consoles introduce some hologram or some other tech that puts you in the game in a different way than looking into a TV, this thread fails.












