The longest economic downturn since the Great Depression has left a lot of older cars on America's roads as cash-strapped consumers have had no choice but to squeeze more miles out of aging vehicles. In theory, at least, that has the auto industry set up for a big rebound in sales.

As Alan Mulally, chief executive of Ford (F), told investors and analysts recently: "We have tremendous pent-up demand. The average age of a vehicle in the U.S. is over 10 years now because people have been delaying this decision for all of the obvious reasons."

But an industrywide pickup won't necessarily benefit all players equally. Market share, after all, is pretty much a zero-sum game in the developed world, and conquering China and other emerging markets is easier said than done.

Emerging-market opportunities, especially those found in China, are a cornerstone of the bullish case on General Motors (GM). After a nearly two-year odyssey through bailout and bankruptcy, storied automaker made a historic return to the equity markets last week in one of the biggest initial public offerings of all time. But as much progress as GM has made, it still faces stiff competition, plenty of looming legacy costs and public distaste with its time as a ward of the state.

Ford has the distinction of being the only Big Three American car company to avoid bankruptcy, thanks to the foresight of management, and it's gaining market share. But after a 40% rally over the last three months, is the stock still a bargain?

Toyota (TM) is putting up strong year-over-year revenue growth in an industry where that's hard to come by, and its stock appears to have put the worst of the recall-related sell-offs behind it. True, its production capabilities are the envy of the industry, but its brand has been tarnished, and the company continues to lose money in Japan and Europe. Whether shares look at attractive at current levels is very much open to debate.

For the bull and bear cases on GM, Ford and Toyota, see the video above.