Halo was outdated the day it came out, the PC FPS genre had already overtaken it. I think I have a fair understanding of the console fps genre and I've been into gaming much longer than I want to admit (Maybe moreso than yourself? It is tough to tell). I've played everything from PD, PD0, Timesplitter series, Goldeneye, Halo 1 and 2, Red Faction (corrected) along with others. So once again I state I fail to see the popularity of it unless people are so unexposed to FPSers on the PC, and see Halo as something unique when it is hampered not only by generic design but also piss poor controls that plague most console shooters. For a console FPS, it is one of the best but that is like being the best of the dung heap, there are far better multiplayer and single player experiences out there for PC.
I'm still failing to see how Gears of War is like RE4 (mainly in reference to gameplay, I fail to see how potentially similar controls between games is promising. If that was the case every platformer since Mario 64 would have been great), they are two completely different games. Perhaps you can enlighten me on the similar aspects besides you shoot things in both games (Yes RE4 is more action oriented but it still has puzzle solving and other elements from the survival horror genre). Everything looks like mindless shooting such as the Halo games (which had some of the most pathetic single player story modes ever) with little in the way of planning (I am talking about single player) which is what I consider mindless. Does not mean it can't be fun but it doesn't appear to take many brains to get through it, just twitch firing at hordes of enemies with ducking built in. If the demo is any indication (I could be wrong about the final game) level design is poor, and AI does not appear to be much better (it seemed way to easy to "sneak" up on some enemies).