I don't know... after HS, I tend to want to see the games in action more before judging them. I did not really compare FoM and GoW, but if pressed... my impression is:
FoM
* Animates really well and smooth even in 1080 (I played it in E3 2006 briefly, but like I said I'm getting tired of FPS so I didn't really pay attention to it). Since then, they said they are going to add more effects (and may be retarget to 720p, don't know). There has been a steady improvement in visuals lately.
From the recent clips, the action is also more hectic than GoW. But I think people are really comparing FoM to Half-Life. That's why there is this feeling of "We have seen this before".
* A few of the latest images and clips showed me large areas, and a sense of scale in FoM. I have not played HL before (although I'm familiar with it), I don't know if there are large levels in HL. So far in GoW, I only saw enclosed areas.
GoW
* I really like GoW's art direction. It's more cinematic and dramatic. Because it has large characters and many many small details, it looks refined to me too. The color palette is more interesting than FoM (which appears dull colored so far, although the alien levels are more colorful). FoM is more subtle. I didn't notice the NPC soldiers are all carrying different equipements and bags until someone pointed it out (in one of the shots).
* I also noticed that GoW camera tend to be hi-to-low or level-off (in an enclosed area). So it may not need to draw far.
But like I said, I'm waiting for both games to be released. I care very little (if at all) for X/10 grading. IMHO, the current FoM and GoW hype are both well deserved. People are just interpreting the screens/clips differently (They see very different things in their minds).
Now that I have seen more of FoM, I hope for good AI in order to have a Halo-like experiences (or supercede it --
). As for GoW, I hope for a good story, and a responsive and more free gameplay.
EDIT:
Scooby, I just thought of something. The FoM background seems to show more variety of structures and skyline. The GoW ones I have seen are pretty detailed, but due to the camera angle, I don't remember seeing any skyline, varied landscape or large structures yet. Just want to say there are probably some grounds for the FoM engine hype.