One college professor, who lectures on The Great Books in Literature, says that 1984 is one of only two texts that encompass what the 20th Century will be remembered for: unprecedented torture. (The other text, by the way, is Alexander Sozhenitsyn's The Gulag Archipelago).
His rationale is:
The 20th Century will be remembered for atrocity: genocide, nuclear war, death camps, ethnic cleansing, weapons of mass destruction. 1984 is a representative text that captures the level of pain inflicted on the individual by the state in the 20th Century.
The 20th Century will be remembered for its attacks upon individual by mass institutions (government, military). Winston's death (or conversion to an unperson) is truly a tragedy of the individual and his powerlessness in the face of mass institutions.
Whereas other books focus on subtle, individual themes, only 1984 captures the total socio-economic, geopolitical, and psychological effects of state-induced torture.
1984 focuses on how technology has mastered the concept of torture and destruction. The 20th Century abused weaponry to no end: chemical warfare, spying, nuclear weaponry, genocide, and detention/torture camps.
1984 focuses on how language can be manipulated to evoke terror. The destruction of language in the novel parallels the death of the individual. Language and thought are extinguished in the novel through language (slogans, elimination of words, propaganda).
I am certain that you will receive much in way of feedback for this particular question. I would say that one strong reason why Orwell's work is worthy of being studied is that it presents one of the most vivid forms of how bad government can be. I have always thought that the vision of government in Orwell's work would galvanize most into action in the hopes of preventing any government from representing what is seen in Oceania with Big Brother. I think that another powerful reason to study the novel is that it reflects how acts in the private realm can actually constitute political resistance. The affair between Winston and Julia is one that operates in the private, but is one that comes to represent political resistance. I think that it is distinctive and interesting to analyze how personal actions can have political and/ or social implications. It is also interesting to examine how personal renunciation can have political dimensions. Winston's renouncing and selling out of Julia is as much political as it is personal. Their meeting in the park is a personally brutal moment, but it is also an instant where the loss of political will is also evident. Finally, I would say that the novel has added meaning given the collapse of Communism. Written at a time when the Cold War was fairly well entrenched in the world, I think that scholarship within the novel can reveal much when analyzing it in a post- Cold War setting.