Star Wars has revealed what makes a Jedi Master - and, remarkably, neither Anakin nor Luke Skywalker qualify. The Jedi Order is traditionally governed by the Jedi Code, and while the core stanza is famous, in truth the Code is a much larger document governing every aspect of Jedi conduct. It provides structure to the Order as a whole.
The Jedi Code is something of a "living document," with every generation of Jedi making their mark upon it. No doubt Master Yoda, the aged and venerated Jedi Grand Master, had a massive impact on shaping it over the course of his 900 years. By the time of the prequel trilogy, the Jedi Code had established six ranks of Jedi, ranging from Initiate to Grand Master. These are laid out in Lucasfilm's recently-published The Star Wars Book, featuring contributions from Pablo Hidalgo, Dan Zehr, and Cole Horton, and surprisingly it seems neither Anakin Skywalker nor his son Luke ever qualified for the rank of Jedi Master.
According to The Star Wars Book, a Jedi Master is a Knight who has taken and trained a Padawan to Knighthood. It's reasonable to assume the Padawan calls their mentor "Master" in part as a mark of respect, and in part as an expression of confidence they will be guided to the point where they have completed the Jedi Trials. This revelation has significant implications for Star Wars lore, because it means neither Anakin nor Luke should rightfully be considered Masters, since their Padawans never became Knights.
In fact, this adds another dimension to Anakin Skywalker's fall to the dark side, chronicled in Star Wars: Episode III - Revenge of the Sith. One of the causes of conflict between Anakin and the Jedi Council was over whether or not Anakin was qualified to be considered a Master, with the Council believing he lacked control of his emotions and was vulnerable to Palpatine's influence. For Anakin, though, the Council's reluctance would remind him of the fact his Padawan Ahsoka left the Jedi Order, having been let down by the Council. These old wounds would have been reopened by his brief reconciliation with Ahsoka just before the Siege of Mandalore, as told in Star Wars: The Clone Wars season 7. The members of the Jedi Council were correct, but they underestimated the emotional cocktail brewing within Anakin's heart.
Meanwhile, it is unknown whether Luke Skywalker ever considered himself to be a Jedi Master, but he certainly allowed others to call him that. According to Charles Soule's The Rise of Kylo Ren, Ben Solo was Luke's first apprentice, and none of his later students had become a Knight before Palpatine destroyed Luke's Jedi Temple. Thus, according to the Jedi Code, Luke Skywalker cannot be considered a Master either. Oddly enough, his sister Leia has more of a claim to being a Jedi Master than either Luke or Anakin, because she trained Rey for a year before Star Wars: The Rise of Skywalker, and Rey did indeed go on to become a Jedi Knight.