Well, if Rome's various enemies had supported Hannibal as they had promised he would have been in a very strong position. But believing they would have simply replaced the Roman Empire with a Carthaginian one the stayed at home. In hindsight we can all see this was the wrong choice as Rome quickly conquered the lot of them after Carthage sued for peace.

The thing with "what if" questions is where do they end? You have limitless possibilities almost by definition, so my answer to the original question is yes. A new Alexander could have re-united his predecessor's empire. A new Pyrrhus could have burnt Rome to the ground and Carthage too.