When one reads Mahabharata in its current form, it is always made amply clear that the Mahanayak - the supreme hero - of this epic is Lord Krishna. Although Krishna appears on the scene much later after the feud has happened, he is almost always at the center of the story - and as Krishna is the supreme hero, so is his greatest devotee and friend Partha Arjuna. So much so that Arjuna is considered to be the incarnation of Nara, the supreme Man, and Krisha is considered Narayana - the Supreme God (Vishnu).
Arjuna kills all the Maharathis (generals if you please) in the war --- Bhishma, Drona, Karna --- except the Kaurava brothers. The Kauravas --- all 100 of them, including Dussasana and the eldest Duryodhana --- are all killed single-handedly by - and this is where we come to the second greatest character - Bhima.
Bhima is known for his prowess with his favorite weapon the mace (gada, in Sanskrit), just as Arjun is known for his archery. Bhima is as much responsible and central to all the events of the great epic as is Krishna. He saves his four brothers and mother Kunti from certain death in Lakshagriha. He kills Hidimb Rakshasa, and Bakasura at Ekchakra. The advice that Krishna gives Arjuna in the form of Gita is given to all Pandavas much earlier by Bhima - albeit in a shorter form.
Indeed, there is a school of thought that Bhima was the real Mahanayak of the epic earlier --- this theory is expanded in much greater detail by Dr. P. V. Vartak in his Marathi book 'Swayabhu' ("The Self-made").
Both are born when their fathers were in exile / hiding.
Both these events have a potential of turning really ugly for the Pandavas - like sister Hidimba could have got furious and killed all the brothers as a revenge, and the Yadavas could have waged a war against Pandavas at Indraprastha, where Arjuna took Subhadra. However, both the events turn out to be good for the Pandavas - and end up in matrimony.
Both fight the Great War on the side of their fathers - the Pandavas - and are legendary for their bravery and the havoc they created for the enemy side the Kauravas. Ghatotkach fights shoulder to shoulder with Dhrishtadyunma, Pandava's commander in chief, and is known to be one of the fiercest warriors on this side. Abhimanyu is so proficient in warfare than Kauravas think that there are not one, but two Arjunas - the first being the real Arjuna and the second being his great son who resembles his father in prowess and valor.
Both die tragic deaths in the Great War.
Indeed, these two death are crucial, landmark, and cornerstones in the war, and ensure the victory of Pandavas.
The death of Abhimanyu is much known and celebrated --- the way he takes charge of breaking on his own the Chakravyuha created by Drona when Arjuna is gone away to fight with the Samsaptaka army, how he breaks into the Vyuha, how the other Pandavas are stopped by the barely-known Jayadratha (or Saindhava) by a quirk boon given to him by Lord Shiva that he will be able to fight the four Pandavas (except Arjuna) for one day, how the Kaurava warriors crowd around him, how Karna breaks Abhimanyu's bow from behind, how he charges towards Drona with a chariot wheel --- the images of this battle form a poignant tale in itself, and Abhimanyu's name is considered synonymous with fearless bravery and valor.
In any case, coming back to Bhima and Arjuna, the current versions of Mahabharata give a far more elaborate emphasis on Abhimanyu's death as compared to Ghatotkach's death, which I think is an injustice. In fact, there is an overall tendency to show Ghatotkach as lesser than Abhimanyu, just as Bhima is usually depicted as a hero lesser than Arjuna.