Dat X visor.
Could have been neat. I've always thought that a Metroid Prime-esque approach to Mega Man would be awesome. Looks like someone in Capcom thought the same.
EDIT: watching the rest of the videos, this definitely could have been lots of fun. The music sounds great too.
And again, DAT X VISOR. I can't get over the X visor. I think it looks all kinds of neat. the "finisher" move involving ramming into the enemy and unloading into them or ripping their roboguts out definitely looked cool. The idea of a Human cop sidekick with the idea being that at times the Robot would seem the more human of the two, sounds like it could have been real nice.
Zero killing Power Hungry X? Hmm. Now that sounds mighty familiar... Who knows how their trilogy would have worked out storywise though.
Still, a shame this never happened.
Gritty though? doesn't seem that gritty to me. Still looks pretty vibrant. I mean come on, you've got a guy in a bright blue suit of armor with a glowing red X on his face.
the idea of the gun forming around his hand from his arm seems like a nice mix of classic arm cannon and post-Zero series gun busters