Ask the critics about the best movie of the year and the answer will be nearly unanimous: Kathryn Bigelow's "The Hurt Locker," a jarringly violent look at an Army bomb squad in Iraq.

Ask the folks who actually pay for their tickets, however, and they'll tell you it's James Cameron's "Avatar," a high-tech fantasy-adventure that recently became the top-grossing movie of all time.

These two films, widely considered the front-runners to take home the best picture Oscar March 7, couldn't be more different. They provide an unusually stark example of the choice that voters of the Academy of Motion Picture Arts and Sciences face every year: Should the "best" picture be the most intelligent and thought-provoking? Or should it be the most enjoyable and entertaining? In short, are the Oscars about art or commerce?

Over the years the pendulum has swung rather wildly. In 2008 the best picture Oscar went to "No Country for Old Men," an enigmatic literary adaptation from the Coen brothers. By contrast, last year's winner was "Slumdog Millionaire," an action-romance that featured a Bollywood dance number. Over the decades the award has gone to subtle dramas (1980 winner "Ordinary People") but also to slam-bang epics (the 2000 film "Gladiator").

That unpredictability keeps the Oscars exciting — at least sometimes. In past years, audiences have been tuning out the annual awards broadcast on ABC, partly because the nominees have been critical rather than popular favorites. Who wants to stay up late and root for a movie you haven't seen? Last year's show drew about 36 million viewers, compared to the 55 million or so who watched in 1998, the year "Titanic" won.

In response, the academy this year expanded the best picture field to 10 nominees, up from the usual five, in the hopes that more well-known films would make the cut. As a result, the 10 nominees include not just serious-minded fare like the urban drama "Precious: Based on the Novel 'Push' by Sapphire," but several blockbusters whose grosses topped $100 million. Among them: the heart-tugging sports movie "The Blind Side," the sci-fi flick "District 9" and the animated crowd-pleaser "Up."

"I've been saying this is the populist Oscars," says Harry Medved, spokesman for the movie-ticket service Fandango. "The fact that you've got movies that are huge box-office hits for best picture means that finally, the awards will be relevant to TV watchers around the country."

In decades past, this didn't seem to be a problem. In the 1940s and '50s, the major studios reliably produced well-written, star-studded crowd-pleasers. And the winners really did seem to be the cream of the crop: "Casablanca," "All About Eve," "From Here to Eternity." In hindsight, at least, it's tough to imagine feeling disappointed or alienated by such Hollywood high-water marks.

It wasn't until the '60s and '70s that movies, like the overall climate of the country, became a little more challenging. As highbrow foreign films made inroads into American culture, the Oscars began nominating edgy, difficult movies like the ultraviolent "Bonnie and Clyde" (1967) and Robert Altman's semi-experimental "Nashville" (1975).

In 1977 the best picture nominees were particularly striking: the Watergate expose "All the President's Men," the cynical satire "Network," Martin Scorsese's blood-soaked "Taxi Driver" and Hal Ashby's "Bound for Glory," about folk musician Woody Guthrie. (The winner, however, was "Rocky.")

That turbulent era reinforced an Oscar truism: Voters tend to favor timely, topical or issue-oriented movies. Among this year's nominees are the recession-themed "Up in the Air," the sexual-abuse drama "Precious" and the race-conscious sports movie "The Blind Side." Even the popcorn flick "District 9" can be read as a political allegory for South African apartheid.

"From the beginning, the academy members have always gone for the Important Movies," says film critic Leonard Maltin.

That explains the nomination for "The Hurt Locker," which directly addresses America's war in the Middle East. "The Hurt Locker" could become the first war movie of any kind to win the top Oscar since Oliver Stone's "Platoon" in 1987.

"Avatar" also counts as an Important Movie, though in a very different way: Its motion-capture techniques, groundbreaking 3-D effects and computer animation — all brought to unprecedented levels of sophistication — may open new doors to filmmakers.

Maltin isn't alone in calling the approximately $230 million film a game-changer, although for now it's a game few directors can afford to play.

As of last week, several Internet betting sites had "Avatar" as the odds-on favorite, followed by "The Hurt Locker."

Either way, as long as viewers tune in, the big winner will be the Oscars themselves.