Like most people, you are minimizing the FPS genre and the evolutionary paths the sub-genres have followed.
I would argue, factually, that FPS continue to evolve more so than most other genres.
Just in the last decade we have seen the genre evolve in a number of directions (in general order my loose memory of the order I saw them introduced).
Look at input/interaction which started as simple WASD and then evolved through Mouse Freelook and Straif; Crouch/Jump/Use; Lean Left/Right/Prone; Cover.
Gameplay has also evolved on an objective level, first starting with Find Key, Find door, kill everything; progressing to basic NPCs and stories; RPG cross overs; unlinear maps; multi-pathed games; and now even the "movie" story game with very detailed facial animations, body gestures, and lip syncronization.
Multi-player is probably the most easy to grasp for those who are FPS noobs. The first FPS didn't even have multi-player. Then we were introduced to Deathmatch and Coop. But it didn't stop there. There began a number of new modes -- team and individual -- of deathmatch, elimination, king of the hill, tag, keep away, and so forth. But that wasn't enough, then we began seeing multiple forms of "objective" style MP scenarios, from "hold the control points" like Battlefield and DoD to more "objective" driven MP as found in games like UT and Timesplitters. And then we can add in free roaming maps, and more importantly, vehicles. We have gone from no vehicles to having land, sea (above and below), and air (fixed wing and other) vehicles that can be manned by players in realtime in conjunction with traditional FPS grunts--or even merged with copilots and gunners. And I haven't even begun discussing Class Based gameplay with the infinate number of varieties for balance OR the balancing of weapon loadout/controls (e.g. some games allow unlimited number of weapons, others only 1 or 2; some games like Halo allow you to toss a grenade at other times and encourage melee and so forth).
And there have been many variations, alterations, and tweaks of the above scenarios -- and this is just the tip of the iceberg. Just in 2004 the "big" FPS games (Doom 3, Far Cry, Half-Life 2, CoR, Painkiller, etc) demonstrated how a variety of FPS can develop -- and use -- technology in vary different ways to get different results.
If you are building games ONLY around new "whiz-bang" technologies your game is gonna SUCK.
The point of a great game is to build a balanced game, that is fun, and uses technology to present an experience that is enjoyable and draws the player in without being flustered, frustrated, or annoyed. Typically a lot of "technology" based gameplays totally fail at deliveraing a good game. This was true of Physics (something you mentioned) until HL2, and even then a special scenario of gameplay had to be invented (grav gun and block stacking, etc) to accomodate it.
But should we be so niave to believe that every game from now on should take the same approach to physics? It worked for HL2; but in Gears it would be a gimmick. Again, are you trying to show off technology OR build a great game?
Being a great game doesn't require inventing and introducting 10 new technologies and basing gameplay around them. A game is a sum of parts all relating to Gamer Experience. Gears IS doing many new things in the FPS genre and looks to be a totally new conceptialization of the genre in MANY ways.
Obviously there will be those complaining, "Why not use their uber GFLOPs for some new radical new technique to change gaming" I think the fact stands that FPS gamers... gasp... want and FPS that works. If Epic has spent their resources coming up with a new way to experience FPS by changing the balance, pacing, and conceptialization of the genre -- something unseen on previous consoles -- I think any arguements about "technical-driven gameplay elements" missing from the game really miss the point. Case in point:
