The visionary doesn't need to have the CEO title - it's even counterproductive to put the burden on the visionary capable I think. CEO needs to build a structure and culture around him/herself that allows the others to do what they do best.
Hence when it comes to product related "visionarism" the CEO must be capable to recognize visionary talent in the area (far from easy if he's got none him/herself) and learn to listen to it using a fairly direct channel not clouded by company politics (also far from easy in some corporate cultures) to build a shared vision that
a - works in the market
b - stops following others and leads on its own merits
c - the CEO can defend when taking to analsist, stakeholders, press, employees, and whatnot
So he has to make it his/her own, even if (s)he didn't figure it out by him/herself.
I'm pretty sure Mr. Gates never had much product vision - never seen evidence of it beyond having a far to harsh business "shark" mentality for my taste. Anyway I feel people credit him for too much he simply stole elsewhere. [Now knowing what to steal and whatnot can be considered vision of a sort too, it's just not my definition]
From the looks of things Steve jobs might have developed the sense over the years (I'm pretty sure he did not have it in the Apple ][ days), but I also know how strong a performer he was (saw him while he was working for NeXT) on stage that it's hard to tell if he learned to listen to others and make it his own or if he sourced it himself. It's also not important: he did! Still, I hope it's the former and I hope the visionaries he relied on are (still) at Apple and that Tim Cook is learning to listen to them (appearances are that he is) and make the transition to make it his own (not there yet AFAIK).