But this time it's different! Maybe!
I think the shift in the design of the Xbone and PS4 toward pretty much mimicking the specs of a mid-high range game PC is going tamp down the possibility of unlocking a "wow" factor not apparently possible in early gen games. Like, I kind of doubt there's going to be a Gear of War-style eye-opener. The specs are what they are out of the box, and while they'll surely be juiced and optimized as much as possible, there is less potential for crazy work-arounds and breakthroughs in programming for weird proprietary boxes. (Factor 5, for instance, did some crazy crap with the Gamecube that Nintendo was unwilling to try for their own titles.)
Separately, there are fewer low-hanging fruit. A lot of the new extra juice goes toward higher resolutions and framerates (which still aren't hitting 1080/60FPS for many "next gen" games) and improved anti-aliasing, which don't make a startling difference for most people, myself included.
I think the best chance for something truly impressive happening (outside of super-pretty corridor/cinematic presentation crap that remains less interactive than many PS2-era titles) has to come through design. Using the extra power to design a gameplay concept that wasn't previously possible, even if it doesn't look technically stunning. Dead Rising with moar zombies isn't going to cut it. Maybe pick up the advanced physics baton from Half Life 2, where it's been gathering dust? Work on an advancement in AI, where it's been gathering dust since Perfect Dark? Something interesting with time beyond short-term rewinds? I dunno. But right now all I'm seeing from next gen is superficial visual enhancement and trying to jam online social experiences down the throats of as many genres as possible.