I feel his strength was being an endless fountain of interesting ideas combined with ability to inspire lots of hard work from his development team. I forget if it was Dungeon Keeper or Black and White where they talked to the development team while he was on a junket and they had no idea about of a bunch of the features he was promising. Ultimately I think he had a really talented team at Bullfrog who slowly burned out and over time people were less willing to kill themselves on death marches trying to carry out his whims.