It looks much better in motion than it does in those screenshots, but it's still hard not to miss all the detailed, atmospheric textures of the original. To be fair, though, it's an intentionally different art style (which coincidentally does happen to blend in quite well with the bright cartoony style of all the other games, but that's another story), and probably one that works better on a handheld than would a darker, more texture-heavy style, lending greater visibility to help balance out the smaller, usually less brightly-lit screen of the 3DS as compared to a TV.
Though that again raises the question... why not make it on Wii U?
It'll be a good game, I'm sure, but... different. And I don't like things that are different. Every Luigi's Mansion sequel should be exactly like the original, because I don't like things that are different.