We first need to answer one question. Why are the writings of Isaiah, Jeremiah and Ezekiel referred to as the major prophets while others who wrote, such as Jonah, Joel and Malachi, are considered "minor?" It is not because the life, or the books, of Jonah and others were considered less significant or impacted less people than writers such as Jeremiah or Isaiah. It is primary because their books are significantly smaller.
For example, Ezekiel's book (the smallest of the "big three"), contains forty-eight chapters while the two largest books written by those considered the minor prophets (Hosea and Zechariah) each have only fourteen chapters. The book of Isaiah has sixty-six chapters.
Daniel's book contains plenty of prophecy-related material. He is not, however, considered one of the Major Prophets. His book, twelve chapters long, was classified as one of "the writings" (along with books such as the Psalms, Proverbs and others) in Ezra's three-part division of the Old Testament.
Isaiah, the first of the prophets considered "major," had an active ministry that centered in Jerusalem. It ran from the last year Judah's King Uzziah ruled (740 B.C.), through the reigns of Jotham and Ahaz, to the end of King Hezekiah's rule in 686 (Isa. 1:1, 6:1 - 8).
The Bible records that during his life he married a prophetess and had at least two sons (Isa. 7:3, 8:3). It was during his ministry, in 723 B.C., that the northern tribes of Israel were conquered and taken into captivity by the powerful Assyrian Empire.
Not only did he write the book that bears his name, he also wrote 1Samuel, 2Samuel, 1Kings and the first half of 2Kings. He is mentioned, by name (the KJV Bible refers to him as "Esaias"), in six New Testament books (Matthew, Mark, Luke, John, Acts, Romans).
The prophet's writing is referenced more than 35 times in the New Testament and he is the most quoted Old Testament writer in the Gospel accounts. He was also a contemporary of Micah, one of the Minor Prophets, who wrote from 740 to 711 B.C.
Isaiah, at one point during his ministry, was commanded to preach naked for three years as a sign that both Egypt and Ethiopia would be conquered and that their people, in the nude, would be taken captive (Isa. 20:1 - 4). He also gave prophetic warnings concerning Assyria, Babylon, Moab, Syria, Ethiopia, Egypt, Edom, Israel, Judah, Arabia, Tyre and even the whole world (see chapters 13 - 21, 23 - 25).
In 701 B.C., during the reign of Hezekiah, the King of Assyria (Sennacherib) brought a large army into Judea and threatened to conquer Jerusalem. Because Hezekiah humbled himself before God and pleaded for help, it was prophesied that Sennacherib would not enter the city and that, when he went home, he would be killed.
The Eternal then sent the Angel of the Lord to destroy 185,000 Assyrian troops! After his bitter defeat Sennacherib went back home to Assyria where he was soon assassinated by his own family (2Chronicles 32, 2Kings 18 - 19, Isaiah 37)!
The prophet also foretold that a restoration of Jerusalem and God's people will occur and they will be made glorious (Isa. 51:3, 52:1). God also revealed to him not only what caused Lucifer to sin and become Satan, but also what will be his ultimate fate (14:12 - 20).
Isaiah is one of a small group of prophets that was inspired to foretell events and, in some cases, offer amazingly detailed information related to the coming Messiah (Jesus).
For example, Isaiah stated the Messiah would be miraculously born from a virgin (Isa. 7:14) and that he would be in the lineage of King David (11:1). He would be born a King destined to rule God's Kingdom forever (9:6 - 7, 32:1). He additionally foretold that the Lord, physically, would not be handsome or have striking features but rather be average looking (53:2).
He foretold of John the Baptist's ministry that would prepare the people for Jesus' coming (40:3). He also predicted where Christ would live during his public ministry (9:1 - 2). Jesus' ministry would draw Gentiles (non-Jews) to it (11:10, 42:1 - 4, 49:6, 52:10) and He would not only heal those who are brokenhearted but also preach deliverance to those in need of salvation (61:1 - 3).
In regard to Christ's suffering and death, Isaiah stated he would be rejected by most people (Isaiah 53:1, 3), considered a criminal (53:12), and ultimately be tortured (50:6, 52:14 - 15). He also prophesied Jesus would willingly offer his sinless life to suffer and die for our sins, and his sacrifice would make possible not only our physical and spiritual healing but also our salvation (chapter 53). Lastly, he predicted that although given the death penalty as a criminal, the Messiah would be buried among the wealthy (Isa. 53:8 - 9).
Jesus himself quoted the prophet near the start of his public ministry and stated he was the fulfillment of his words (see Isaiah 61:1 - 2 and Luke 4:18 - 21). One at least two occasions the Lord criticized some religious leaders by stating they fulfilled prophecies written by the prophet during his life (see Matthew 13:14 - 15, 15:7 - 9).