If I understand the nature of the character you're trying to identify it's a combination of stereotypical (and therefore not especially interesting) hero and average (and therefore not especially distinctive) person. One term that authors sometimes use to describe such a character is heroic everyman. The everyman component of the term, of course, derives from the lead character of the medieval morality play Everyman. Here is the definition for that word in Merriam-Webster's Eleventh Collegiate Dictionary (2003):
everyman n, often cap {Everyman, allegorical character in The Summoning of Everyman, 15th cent. Eng. morality play} (1906) : the typical or ordinary person
Likewise, the Eleventh Collegiate defines everywoman (dating to 1945) as "the typical or ordinary woman."
Though the term "heroic everyman" may seem to border on the oxymoronic, authors use it to define the sort of predictably heroic yet somehow unexceptional normal lead characters in many novels and movies. It seems to have arisen fairly recently. A Google Books search turns up dozens of matches for "heroic everyman," the earliest of which is from 1960 From Earl Rovit, Herald to Chaos: The Novels of Elizabeth Madox Roberts (1960) [combined snippets]:
The structure [of The Time of Man], as a whole, is thus designed to portray the developmental pattern of any man, and also of Miss Roberts' heroic everyman, for as Miss Roberts further suggests, the design of the novel reduces Ellen Chesser to the symbol of man as naked spirit fronting the most essential forces of life:
The design moves downward toward a nadir, step by step, to a sort of bottomless pit of woe. ... The book is an outry. Man, poor creature, loves his ease, his easy religions, his well-filled stomach, his nice prides in little things. ...
The next-earliest match is from eleven years later. From Virgil Grillo, End in the Beginning: Dickens' Sketches by Boz (1971) [combined snippets]:
sublime statue of Pickwick, "the immortal Pickwick," the reader comes to recognize the non-ironic implications of his statements: Pickwick is immortal by virtue of his humble mortality. Because the internal narrator records and points to all of Pickwick's foibles, and yet still insists on his grandeur as a man, the reader eventually transcends the surface irony of the narrator's praise and sees through to the truth beyond the irony. Pickwick becomes an heroic everyman.
Later books apply the term "heroic everyman" to such varied figures as Jack Crabb [Dustin Hoffman] in the film Little Big Man (1971),Macbeth (1981), the actor Jimmy Stewart (1986), Jean Valjean [Colm Wilkinson] in the musical Les Misérables (1987), Charlie Bradshaw of Stephen Dobyns's Saratoga Springs mystery series (1989), the poet Hayden Carruth (1990), the Lone Ranger (1991), Jim Garrison [Kevin Costner] in the film JFK (1991), Esther Summerson in Charles Dickens's Bleak House (1992), Malcolm X (1993), Jack Ryan [Harrison Ford] in the film Clear and Present Danger, (1996), the Mexican cowboy (1996), the American doughboy soldier in World War I (1997), Toussaint L'Ouverture (1999), Bing Crosby (2004), Gordon Freeman of the video game series Half-Life (2005), Don Quixote (2007), Robinson Crusoe (2007), Che Guevara (2007), Captain John Miller [Tom Hanks] in the film Saving Private Ryan (2007), Too Much Coffee Man (2010), Travis Bickle [Robert De Niro] in the film Taxi Driver (2010), Johnny Cash (2011), Othello (2011), Othello (again) (2011), the U.S. news journalist (2012), Robbie Turner [James McAvoy] in the film Atonement (2012), William Harford [Tom Cruise] in the film Eyes Wide Shut (2012), Davy Crockett [John Wayne] in the film The Alamo (2013), Senator C. Estes Kefauver of Tennessee (2014), Bilbo Baggins (2014), Mitt Romney (2014), and John Doe [Gary Cooper] in the film Meet John Doe (2015).
The range of "heroic everymen" on this list suggests that these characters and real-life human beings may have little in common beyond their (in some cases unexpected) capacity to rise to a challenge, and their possessing a sufficiently down-to-earth persona that readers, viewers, and everyday citizens can identify with them. It is certainly not the case, however, that all of these characters are bland personalities of the blank-slate school. Some are quite vivid personalities that nonetheless have some humanizing weakness (such as naivete) that enables others to sympathize with them and even worry for them.
