Selena Halcyon
Jedi Master
Prophecies can also be failed.
One also can look at things another way. The prophecy was intended to see the end of the Sith. He ends the Sith when both himself and Sidious die. After all, this pulls from Obi-wan's understanding of the prophecy that Anakin was supposed to destroy the Sith not join them. This holds very nicely with the idea that balance in the force is the lightside, and that the darkside is corruption. To be balanced is in the light, so destroying the corruption (Sith) balances it.
Honestly, it is hard to argue that Luke actively did anything. He delivered no killing blow. He just was there as a tempting force for Vader to come back to the light. Little more. He was a beacon, but little more. Hard to really argue him fulfilling it, when Anakin still can be argued as fulfilling the prophecy despite his fall.
One also can look at things another way. The prophecy was intended to see the end of the Sith. He ends the Sith when both himself and Sidious die. After all, this pulls from Obi-wan's understanding of the prophecy that Anakin was supposed to destroy the Sith not join them. This holds very nicely with the idea that balance in the force is the lightside, and that the darkside is corruption. To be balanced is in the light, so destroying the corruption (Sith) balances it.
Honestly, it is hard to argue that Luke actively did anything. He delivered no killing blow. He just was there as a tempting force for Vader to come back to the light. Little more. He was a beacon, but little more. Hard to really argue him fulfilling it, when Anakin still can be argued as fulfilling the prophecy despite his fall.