In FPSs, yes, and racers, but what about other genres? Extra control or different control can find it's way to into many situations, whereas the usefulness of rumble feedback is fairly limited in scope. Take my list of other genres, and add what you think rumble can contribute above and beyond what's obvious with audio and visual cues. This is what I can come up with off the top of my head :
FPS
- Warning when taking damage when not obvious
Racer
- Warning of collisions or leaving track, rumble strip
Hack-n-slash
- When you're getting low on health as a warning, save you looking up at the health bar
Soccer
Platformer
Turn based RPG
Fantasy real-time RPG
RTS
- Alert to bring your attention to some else on the battlefield other than where you're looking, such as base is being attacked.
Puzzle game
- Warning for time running low
Party game
As you see, I haven't done very well! And some of those can be easily accomodated by on screen windows or audio alerts. It won't have the urgency of the rumble, for sure, but the purpose of the rumble in these cases can be provided by other methods, such as a warning sound for puzzlers or RTS, a red flash on the screen when you're taking damage in an FPS.
Now if I think what tilt control could add to these genres that cannot be satisified with DS2 and rumble :
FPS
- Camera control, extra player movements, keeping hands on movement and attack buttons
Racer
- Camera control, freelook, (semi) intuitive stearing alternative
Hack-n-slash
- Camera control keeping hands on movement and attack buttons
Soccer
- Camera control in 1 player. Intuitive player shimmying/maneouvring control.
Platformer
- Motion based control without using sticks at all
Turn based RPG
Fantasy real-time RPG
- Camera control, extra player movements, keeping hands on movement and attack buttons
RTS
- Map/camera control
Puzzle game
- Motion based puzzle games like Mercury
Party game
- Whatever mad schemes devs come up with
That's what I'm seeing. Things like a Mech game where you control left arm with left stick to aim, L1 to shoot, right arm with right stick and R1 to shoot, and mech movement by controller tilt also become availalble.
Of the people I know who play games, invariably they switch rumble off. None are FPS fans. That seems the biggest difference to me at the moment. Fans of FPS and racers feel rumble adds a lot to games. Non-fans don't think the same. Totally unscientific observations, mind! Maybe you can come up with your own lists of what rumble adds to these games that improves gameplay over tilt?