In a Q&A interview with Team Ninja game dev Yosuke Hayashi he states the following in response to a question ask to him by Gamepro.
GamePro: Can you talk about the overall graphics and what people can expect technically from Ninja Gaiden Sigma on the PS3?
Yosuke: It's not so much that we brought the game over to the PS3 as it is we more or less are recreating Ninja Gaiden with the most up-to-date graphic techniques in order to take advantage of the hardware. In order to have this be a great experience for both people who are new to the series as well as those who've enjoyed it since the beginning, we want to provide an experience that looks totally new and fresh. One of the best ways to do that was to have a game that runs at a 1080p with a constant 60 fps, and utilizes real-time self-shadowing. No other game as accomplished all three of these goals at once.