I think Garriot was probably a decent game designer who surrounded himself with good talent, but he was bad at managing time and he was bad at managing a company.
He sold out to EA because Origin Systems was tanking, but after he did that I think EA took the reigns away slowly until he just didn't care anymore and the final product (U9) shows his disinterest. Around that time EA was really into UO and I guess they thought they could ride that pony forever.
EA has been trying to do something with single-player Ultima on and off for a while, but they never had the people in place to do it any justice. Bioware/Mythic might have made a good game out of it 4 years ago but now it seems like they're just shells full of group-think and yes-men.