The OEM pads are not necessarily the best pads, but they are optimized to give good stopping performance while staying nice and quiet and providing decent wear/relatively long life. Replacement brake pads are similar to tires in that there are many choices out there and each one represents a compromise of sorts.

If you want better stopping performance (higher friction) you can get that but usually at a trade-off for increased squealing or more dust. The OEM pads are always expensive at the dealer and are the devil that you know. YOu can find those same pads from on-line retailers for less. The TireRack sells pads and they are pretty good at providing real-world advice on performance of particular pads (but these will not be OEM type).
HIgh performance pads can stand higher temps before they begin to fade, but will almost always squeal more when cold and might put out more black brake dust.

Also, new rotors are always a good idea when putting on new pads as stopping ability is a function of how much heat the rotors can absorb and that is a function of the mass (amount of cast iron the rotor contains) and worn rotors have lost some mass. So new rotors will have more mass than old, worn rotors. Getting the rotors resurfaced cuts even more mass from them, so they might be flat after resurfacing (getting then "turned") but they won't be as efficient at stopping your car.