If Warsaw, Hiroshima, Berlin, Manila, Seoul, etc. were brought back from the dead, Aleppo will be a cakewalk by comparison.
All of the above cities were all but flattened during WW II and, I guessing Aleppo had nowhere the population losses than any of the above European/Asian cities.
Closer to home: New Orleans had ITS share of disaster with Hurricane Katrina less than 12 years ago.
There is a good chance that Aleppo will eventually be rebuilt at some point in the future however the likelihood of it remaining the city that it once was is extremely small. As with Cologne which was destroyed during the Second World War, the city was rebuilt but as a modern city and not a reconstruction of its former self. The same is likely to happen to Aleppo.
It will take years, maybe even decades, but I believe that Aleppo will eventually be rebuilt. First, the violence must end before any progress can take place. I believe once the violence calms down then builders, architects, and engineers can rebuild Aleppo. It is even possible that Aleppo could be one of the most innovative cities in the world some day.
Aleppo was a huge city, judging from the images that I have recently seen of it. That being said, I do feel the city could be rebuilt in a strong capacity, but I do not know if it could be completely rebuilt and look as it once did in the past.
The destruction of Aleppo has been nigh-complete, but Syria's overall oil production capacity is high enough that it is possible for them to finance the reconstruction of Aleppo within the next three decades. So long as foreign powers do not install an external ruling body in the nation - and so long as the current conflict ends within the next ten years - most of the damage will be recoverable.