Lightwave. And I'm not just saying that 'cause this is 'SimplyLightwave.com'. I've tried 'em all, but Lightwave is the easiest and the best. And by easiest I don't mean 'dumbed down', it's just highly intuitive.
Also, it's worth noting that Lightwave is about the most used package in Japan...and if there's one culture in the domain of humankind that knows the most about animation as a medium, I think we can all agree that's it.
