IGN has written a fairly lengthly article about the History of SEGA. Most everyone is familiar with the company’s history starting with the Genesis, but there is quite a bit more to SEGA than that.

There will never be another SEGA. While their reign as a first-party has long ended, and the name hardly carries the cachet it once had, the industry owes deep debt to the former giant. An innovator and an unrivaled creative powerhouse, they were perhaps the greatest single developer in gaming history.
While rival Nintendo has shown an unmatched ability to maintain a small handful of blockbuster series, SEGA churned out brilliant original franchises one after another with such frequency they made it seem effortless. Their hit series were practically disposable, because they knew the next one would be just as good. All across the world, from Tokyo, to San Francisco, to Lyon, their studios always bet on the gamble, always took chances, and to their fans, they were always winners.
Unfortunately, SEGA didn’t win many battles in the hardware market. Their history is riddled with mistakes – some that you probably know well, and a few you’ve never heard before, but all of them heartbreaking. Their moment on top was fleeting, lasting just a few years before it all came crashing down. When SEGA retired from the hardware business, it felt like originality and creativity had lost the battle against bigger brand names. SEGA’s way of doing business didn’t pay off, and even as a third party they’ve continued to struggle.
As SEGA’s star has faded, some are quick to whitewash their history; to act as if their success was the fluke and their failure inevitable. It’s natural – the victors always write the history books – but that isn’t the way it happened. This is the story of SEGA; the good, the bad, and the possibilities of what could have been.