"Best" is pretty subjective, though I'm not aware of a particularly rabid DDO following I'd say that this isn't a lot different than asking which game console something thinks is best or which political party they think is best.
If you're speaking strictly in terms of design and polish, I don't think there's any question that WoW is "best", given that it's had millions of development man-hours poured into and billions of hours put into it by players. DDO just can't compete with that, although it appears to be fairly well put together.
