NEW YORK — His smile is as wide as the Amazon when Charles Gibson is asked simply whether he’s having fun.“I’m having a great time,” said Gibson, marking one year as ABC’s “World News” anchor this week. “I’m loving it. I really love doing this.”

ABC News loves having him. Gibson is thriving at a job he thought he’d never have, at a time he thought he’d be retiring. “World News” has swept past NBC’s longtime leader “Nightly News” in the ratings this year, winning 11 of the past 15 weeks in a turnabout so sudden it took even Gibson’s bosses by surprise.

The evening news may no longer be what it once was, but it’s still a network news division’s flagship. First place is a valuable point of pride.

“He really loves the news and reporting the news, and I think that comes across,” ABC News President David Westin said.

Gibson, 64, says he’s an accident of history. He figured his 30-year ABC career would be over before Peter Jennings left as anchor, but Jennings died of cancer in 2005. Westin then passed over Gibson, turning to him after Bob Woodruff was severely hurt in Iraq and Elizabeth Vargas became pregnant.

He joined a broadcast with experienced leadership tested by tragedy. His top producer, Jon Banner, has held the job more than four years. That contrasts with his rivals: NBC’s Alexandra Wallace took over three months ago and CBS’ Rick Kaplan began trying to right Katie Couric’s ship this spring.

Gibson is surrounded by strong reporters and his show has “a wider range of moods” than its rivals, said Andrew Tyndall, a news consultant who monitors content of the evening news. The inspirational feature that ends a broadcast is almost an evening news cliche; “World News” is just as likely to end with something quirky, he said.

It also doesn’t hurt that Gibson is competing against two people in their late 40s in one of the few TV arenas where gray hair isn’t considered a handicap.

“Charlie most resembles the type of individual who most of the audience has been accustomed to getting the evening news from for the past 20 or 30 years,” said Erik Sorenson, a former MSNBC president and once NBC anchor Brian Williams’ boss. “He’s the closest in age and look to the Peter Jennings and Tom Brokaw mold that has been winning in the ratings for as long as we can remember. I think it’s as simple as that.”

Gibson talks of the broadcast in almost holistic terms. He said he’s learned to place less emphasis on the lead story and incremental stories that would take too long to explain. And his own experience comes into play, too: “World News” placed comparatively less emphasis on the Rev. Jerry Falwell’s death partly because Gibson knew him from his reporting days in Lynchburg, Virginia.

What’s most important is leaving viewers with the feeling that it was a half-hour well-spent, he said. He opens each show by saying, “welcome.”

Some theorists believe Couric’s arrival at CBS caused evening news viewers to switch around and sample different broadcasts more than usual, and this benefited Gibson. By starting its prime-time election night coverage a half-hour earlier than NBC and CBS, ABC News had an important victory and gave Gibson more exposure.

Still, explaining ratings fluctuations is a lot of guesswork. NBC’s severe prime-time problems — it’s a distant fourth while ABC is trending up — may be taking a toll elsewhere on the network. It’s worth noting that on the last big news week, following the Virginia Tech shootings in April, Williams won.

Gibson hasn’t lost since. It had to be particularly alarming to NBC that on the mid-May week when Williams scored an exclusive interview with British Prime Minister Tony Blair then returned to New Orleans, site of his biggest triumph as anchor, ABC won by its widest margin since 2001. “World News” also did a three-part special on Darfur that week, hardly a ratings-grabber.

Two characteristics of Gibson’s work have subtly reinforced the weak points of his competition.

Gibson started with none of the fanfare that preceded Couric’s arrival at CBS News. He essentially shrugs when asked how he’s put his stamp on “World News.”

“There are things that I’m probably more interested in and that gives us more of a bent in one direction,” he said, “but I’m not aware of them. The paradigm for these shows is 50 years old and we’re not going to change that. You maybe work around the edges.”

Compare that to Couric, who came in with a mandate from her bosses to shake up the evening news format. CBS found no one was interested in shaking.

Off-screen, Princeton man Gibson is more buttoned-down than Williams, a genuinely funny man with modest roots. On-screen, it plays to the opposite. Williams is more likely to sound like he’s talking at you, while Gibson is talking with you.