They're older than Nintendo, as far as console gaming is concerned, so they command a certain respect for still hanging in the game.
They don't take much risks nowadays, but they're pretty much solely responsible for how the current generation of consoles was defined, even though they dropped out early.
They were always the first competitor to leap to a new generation of gaming and constantly pushed it forward.
Sega deserves respect and deserves better than their current lot in life. Their exit from hardware is of the many reasons I hate Sony, irrational though it may be.
In many ways, though, I feel MS is trying to be Sega's successor, especially with what's been released about the Xenon/XBox Next/XBox Pandapus/whatever. They're going for first without trying to turn the industry into something it's not like Sony seems to have in mind. And while it doesn't have many great games, the XBox was a great system. MS isn't Nintendo, trying to find ways to revolutionize gaming, but they aren't Sony trying to find ways to corrupt gaming either.