Eric La Flèche, the CEO of Metro, a Canadian grocer, has been instrumental to improving margins. When he took the helm in 2008, the firm's profitability was average. Since then, it's improved almost every year and is now the leader.
This a sparkling example of the power of having a strategic leader take over the reins of a company. Given that he joined in 1991 as General Manager, Real Estate Development, and has since then held various management positions, it's no doubt he knows the company inside out and is best positioned to make the needed changes.
True, the CEO role is so important and often overlooked just because a company is "big". But at the end of the day how the company looks in 5, 10 years depends on where the CEO is steering the ship.
Vision is as vital at a start-up, as it is at a larger or full-fledged mature company, and the ability to execute said vision will come down to the jockey steering the horse.