NEW YORK (FORTUNE) - There was a time when Wall Street treated the CEOs of the largest media companies almost like demigods.

The heads of Viacom (Research), Time Warner, News Corp., (Research) and Disney (Research) predicted that revenues from their films, television shows, cable networks, and magazines would keep pace with the swiftest growth companies. Investors nodded worshipfully and loaded up on their stocks, expecting to be richly rewarded.

No longer. In the past five years shares of the Big Four media companies have underperformed the S&P 500. Viacom's total returns were 37 percent lower than the index in late November. Time Warner's results trailed the S&P by 70 percent. News Corp. CEO Rupert Murdoch felt the need at his recent annual meeting to empathize with shareholders about his company's stock market performance: "It pains us, as it pains you. We are living in -- certainly as far as media goes -- a bear market. You can't ignore that."

Murdoch and two of his peers act as if redemption is only a deal or two away. News Corp. recently spent $580 million to purchase the parent company of MySpace.com, a fast-growing social-networking site focused on teens. Time Warner's Dick Parsons has Google and Microsoft vying to enter into a partnership with AOL that would vastly increase its Internet advertising revenue. Are investors excited? Not really.

Viacom's Sumner Redstone has taken a more radical approach, proclaiming that the age of the media conglomerate is over. He is dividing Viacom in two -- a so-called growth company, comprising MTV Networks and Paramount Pictures, and an entity made up of CBS, Infinity Broadcasting, and Simon & Schuster that will pay sizable dividends and, it is hoped, appeal to risk-averse value investors. Redstone has modestly said he is "pioneering a trend."

That remains to be seen -- investors didn't rush out to buy Viacom stock. Nevertheless, shortly after Redstone made known his Viacom plans, financier Carl Icahn, representing a group of Time Warner shareholders, embarked on a campaign to pressure the world's largest media corporation (the parent of FORTUNE and CNN/Money) to break itself up. Investors didn't snap up relatively cheap Time Warner shares either. It seems the era of the media conglomerate may be lengthier than Redstone anticipated.

The only one of the Big Four that is inspiring a modicum of investor optimism is Disney. Analysts say this is largely because Bob Iger recently replaced Michael Eisner, the imperial CEO who spent his last days at the Magic Kingdom fighting with directors and shareholders.

Iger chose early on to define himself not just as the anti-Eisner but also as a CEO willing to shake up his company, entering into an agreement with Steve Jobs that allows Apple to sell episodes of Lost and Desperate Housewives on the iTunes Music Store. Since then, Disney's total return has risen 6 percent. Is that just because of the iTunes deal? Maybe not. But investors are enamored with companies that can create a market for online entertainment when a large number of people are still getting songs and movies for free through peer-to-peer networks.

NBC Universal has announced a similar deal to sell shows from its broadcast television and cable networks on iTunes. Will Parsons, Murdoch and Redstone follow suit? It may be that moving the merchandise -- not doing more deals -- is the only way for them to get back on their pedestals.

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