I use Autodesk 3DS Max for animations, and it seems to work quite well. It even has most of the common stuff pre-programmed, such as humanoid skeletal heirarchy and customizable walking/running animation. If you have access to Max, I would say stick with that.
As for Poser, I doubt it would be very useful for creating animated game characters, just because the models tend to be super high-poly. It is possible to reduce the poly count (as I outlined in the wiki), but if you tried to do that for each keyframe, the polys on the reduced keyframe models wouldn't match, so you couldn't use them for animations.
If you'd rather go the free route instead of buying an expensive modeling program, you could try Blender. I've never personally done animations with Blender, so I can't say how easy it is. But it is free.