People hate on John Romero because people get to be cocky when they deliver, and he did when he was with Carmack, but when he left to found Ion Storm, he managed to piss off the audience with a lot of mistakes like the delays, the undelivered promises (of course the infamous ad wasn't his fault, but it was his fault not to do something about it, that kind of publicity was like a WWF/WCW wrestler promo back then), it was too much hype for a game that - not counting the technical probelms - looked old next to Quake 3 and Unreal Tournament when it came out...
But why Romero and Carmack worked? the reason is the same why Lennon and Mccartney worked, because both had talent differences that complemented each other... Romero has cool storylines, a sense of involvement, creativity about the art design, Carmack has the tech brains, he pushes the boundaries of game development and his engines are brilliant... And of course, when they separated, Carmack still could do games with great tech, but they lack the Romero spark (like bringing Trent Reznor to do the Quake soundtrack, that was epic), and Romero had this idea of gaming revolution, but without someone like Carmack, that vision got cut and never was fully realized...
