Why was Hannibal considered one of history's greatest generals/strategists? I mean he gave the Romans a lot of problems but he wasn't the only one to do so (Gauls, assorted barbarians, etc.) He also eventually lost to Rome anyway. I acknowledge he is a good military commander but why is it in a lot of documentaries I watch he is considered such an eminent general alongside the likes of Alexander and Caesar?
Most of what I will discuss is based on Polybius' writings (Histories Book 3).
Hannibal was a brilliant tactician due to many reasons. He was aware of the strengths and limitations of his army and the Romans. The Roman army was largely infantry based and had a notoriously weak cavalry up to and including the 2nd PW while Hannibal had a relatively strong cavalry. The strength of Hannibal's cavalry was often used to quickly dispatch the Roman cavalry followed by a swift flanking maneuver on the remaining Roman infantry. Further evidence of Hannibal's sheer brilliance can be found in the famous battle of Cannae, where Hannibal deliberately ordered his weaker soldiers to the middle of the formation and his veteran soldiers on the wings. The veteran soldiers effectively pinched the Roman lines coupled with the quickly victorious cavalry.
Hannibal also usually avoided head-on offenses against the Romans and tended to choose locations and situations that were favourable. For example, the famous ambush at Lake Trasimene was absolutely devastating as Hannibal trapped the Roman forces against the water and hillsides. Furthermore, the complexity with which Hannibal planned battles was extensive, such as the Battle of the Trebia, where Hannibal's brother Mago effectively ambushed/flanked the Roman forces.
Sorry that this was so glazed over and brief; I have to head to class! Hopefully I helped answer your question though.
http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Polybius/3*.html