With the half-century-old ritual of broadcast networks presenting their fall television schedules to advertisers taking place this week, television executives will be looking for signs of one network that can break out of this season’s ratings pack.

After a 2004-05 TV season characterized by near parity among ABC, CBS, Fox and NBC, which network emerges as the dominant player come fall could depend in large part on whether one of them can come up with a promising sitcom to revitalize the genre.

ABC managed to break out of fourth place with the success of shows unveiled at last year’s upfronts, such as soapy dramedy “Desperate Housewives,” which has paved the way for more character-based hours than procedurals.

Despite NBC’s slide from the top spot to fourth place in the adults 18 to 49 demographic this season, the network’s entertainment president, Kevin Reilly, said parity is good for the broadcast business as a whole because it is a sign that a number of networks have shows that work.

“It speaks to the success of network television,” he said. “We’ve seen more hits emerge in the course of one season than we have in years … most notably scripted hits.”

Mr. Reilly said that while every network has a night or time period to crow about, the lack of a leader also makes life harder for broadcasters, but it can be easier for advertisers.

“For the [network advertising sales] marketplace, it’s good to have a pacesetter,” he said. “Parity gives the leverage to the buyers. The four-net share is probably going to be flat. Other than that, it’s a good year for network television.”

One Hollywood talent agent said the network business may be starting a new era in which there is no market leader.

“There is no longer a network with across-the-board dominance,” the agent said. “That’s a huge change. It used to be NBC was dominant, and maybe one night was off. In a fractured universe of not only 500 channels but the Internet, movies, video games, DVDs, that makes sense. People are not coming to a big brand, but coming to specific shows they want to see.”

Mark Hoebich, CEO and founder of the development tracking firm TVTracker.com, said that in the current marketplace, people need to rethink how they define things.

“You’ll still have dominant networks; it’s just the definition of dominance has changed,” he said.

Mr. Hoebich cited as an example Fox’s “American Idol,” which virtually on its own took the network from fourth to first place for the season in the demo.