This might already be kind of irrelevant given how wild this discussion has become but I'll throw it out there- a cell phone will probably never come close to a dedicated handheld light, at least barring some as-of-yet-undiscovered new physics. The actual LED on the die is just part of the system. It's unlikely that a manufacturer would be able to fit the kind of die needed to match the output of a tactical light. But even with the same emitter it wouldn't perform the same. A light is a system made of many parts. First you need battery capacity and voltage. Probably a cell phone can do that albeit with some heating and endurance issues. Heat is another big one. Powerful lights are most often metal which serves as a heat sink. The Malkoff light engine previously mentioned actually included a huge brass heat sink, and it's backfilled with thermal epoxy to mitigate shock and control heat. The last part is the light engine. Potent lights from Cloud Defensive, Elzetta, Malkoff and Surefire use computer-designed reflectors or optics purpose built for a task. An 'orange peel' reflector will create a somewhat diffuse light whereas a TIR system will tend to have a more focused beam. Elzetta uses a solid acrylic optic that protects the emitter and focuses the light. Unless new physics is discovered you need to focus or direct the light, usually through reflection or diffraction. Look at a rifle scope as an example. You can't physically get, say, 30x magnification with a 200 foot field of view at 100 yards, optics doesn't work that way. Designing for one attribute generally is done as the expense of others. If the light die on your phone could output 2,000 lumens it would be very low candella without some kind of lens, and a lens on a phone can only be so deep in practical terms. That's one reason there are stick-on lenses for your iPhone, to create a focus no possible on the CCD die. So yeah, you could create a shallow ring of fresnel-type reflectors but you can only do so much. And this ignores the fact that virtually no phone maker would find it financially sane to try to engineer this into a consumer phone.
Beyond that there's practicality. I always have a flashlight in my pocket and occasionally have had to use it to help a coworker change a tire in the winter. If you ever do this alone you'll notice it takes two hands and three or four is better still. Do you want to set your phone down in a snow bank or rain puddle to shine on your tire while you work? If you do you're the first person I've ever met that did.
And if you're searching for an intruder, do you have a good method of wielding the phone like a search light while you use it to talk to the cops? Can you use the light to search while you use the camera to record? If you have to fire your weapon do you plan to quickly grasp the phone in your mouth to keep the light on the intruder?
Choosing a phone over a light feels a lot like choosing to use an entire can of Right Guard to hide your BO instead of taking a shower.
I would rather have questions that can't be answered than answers that can't be questioned. - Richard Feynman
When I give food to the poor, they call me a saint. When I ask why they are poor, they call me a communist.- Archbishop Helder Câmara