ExxonMobil (XOM -0.55%) is an undisputed leader in the oil industry. With a roughly $450 billion market cap, it's the world's biggest international oil company (IOC) -- that is, not state-owned. It leads IOCs in nearly every metric that matters, including earnings, cash flow, and returns. While ExxonMobil is a leader in today's energy industry, its ability to maintain its leadership will be a crucial factor in fueling its ability to grow shareholder value in the future. Here's a look at whether ExxonMobil i ...