Ninja Gaiden is definitely the most hardcore and arguably has the best fighting system of all the games. And for people looking for a very challenging game that comes out of the gameplay traditions of the original Ninja Gaidens plus the fighting game genre, Ninja Gaiden is definitely the way to go.
I feel as though God of War comes out of a different tradition. There's no fighting game influence. It's more like a Streets of Rage or Final Fight meets Mario platformer than Ninja Gaiden (NES) or Shinobi (Genesis) meets Dead or Alive or Virtua Fighter. Edit: Personally, I'm more of platformer fan than fighting game fan, which is partly why I prefer GOW. But I definitely appreciate what NG has to offer.
That MS supporting hardcore games bit is ridiculous. MS and Sony, two of the biggest companies in the world, are supporting hardcore gaming. There's really no need to scare your readership into buying Ninja Gaiden in order to keep hardcore games alive.
My Top 5:
Shadow of the Colossus, Metal Gear Solid 3, Shenmue, Skies of Arcadia, Chrono Trigger
My 2 nex-gen systems: PS3 
and Wii 
Prediction Aug '08: We see the PSP2 released fall '09. Graphically, it's basically the same as the current system. UMD drive ditched and replaced by 4-8gb on board flash memory. Other upgrades: 2nd analog nub, touchscreen, blutooth, motion sensor. Design: Flip-style or slider. Size: Think Iphone. Cost: $199. Will be profitable on day 1.
