Opinions seem to vary. Haydock’s commentary, in the Introduction to the Book of Daniel, identifies him as the prophet Daniel. (source) The NABRE commentary on this verse identifies him as another Daniel, “the just judge celebrated in Ugaritic literature.” (source) I don’t know if this is the same person but the Wikipedia article on Daniel (biblical figure) mentions “a legendary Daniel who lived before Noah’s Flood” and is mentioned in the Book of Jubilees. (source)
Ezekiel’s comment was written about 592 BC. His contemporary, Daniel, had been deported to Babylon 13 years earlier. Those Jews selected in the first deportation (605 BC) were young noblemen who already had a reputation of knowledge and wisdom, and this reputation continued to grow after Daniel had been placed in Nebuchadnezzar’s palace.
Daniel might have been somewhat youngish to be compared with Noah and Job, however, that seems to be what is being suggested in Daniel chapter 1.
Ver. 14. Job. He and Noe[Noah] were dead, yet undoubtedly interceded for the people, or their names would not here be mentioned, Jeremias xv. 1. (Worthington) — When God is resolved to treat all with rigour, he will save only the just. They shall not be able to protect even their children. But Jerusalem shall not experience such severity, ver. 21. (Calmet) — Noe could not avert the deluge, nor Job the death of his children, neither could Daniel rescue his people from captivity. (St. Jerome) — The first denotes pastors, the second fathers of families, and Daniel such as live continent. (St. Augustine) — All three had been very merciful. (St. Chrysostom, hom. xliii. 1. in Genesis) — Job is placed for holy laymen, and Daniel for people of religious orders. (St. Gregory, Mor. i. 13.) (Worthington) — Hence perhaps Job is placed last, though cotemporary with Moses, as most people suppose. He is not therefore a fabulous personage. (Haydock)
“Noah, Daniel, and Job”: Noah is best known from the account of the great flood, where he is described as “righteous” (cf. Gen 7:1; 6:8); Daniel is probably the name of an ancient Canaanite king of the fourteenth century BC, famous for his uprightness and known to us from Ungarit writings. The book of Daniel, written after Ezekiel’s time, borrowed the name on account of the man’s proverbial probity. Job was also a legendary character, remembered in the book that bears his name as being “blameless and upright” (Job 1:1). All three had this reputation for uprightness, and all three were non-Israelites. By mentioning them here, it seems very likely that Ezekiel wants to give his teaching on personal responsibility a universal character; and he is acknowledging that people outside Israel are able to lead upright lives: “The covenant with Noah remains in force during the times of the Gentiles, until the universal proclamation of the Gospel. (cf. Gen 9:16; Lk 21:24; Dei Verburn 3). The Bible venerates several great figures among the Gentiles: Abel the just, the king-priest Melchisedek—a figure of Christ—and the upright ‘Noah, Daniel, and Job’ (Ezek 14:14). Scripture thus expresses the heights of sanctity that can be reached by those who live according to the covenant of Noah, waiting for Christ to ‘gather into one the children of God who are scattered abroad’ (Jn 11:52)” (Catechism of the Catholic Church, 58).
Still, the passage is a call to the faithful to fulfil commitments they made to the Lord: “Those righteous men, who were wholly just, could not free their own children from slavery: how shall we enter the Kingdom of God if we are not faithful to the pure, unstained baptism that we have received? Who will be our advocate if we have no righteous and holy deeds to our name?” (Pseudo-Clement, Epistula II ad Corinthios, 6, 9).