The other side of it is the actors' interaction with said creatures. Stop-motion animations and CG creatures very often do not inspire convincing interactions from their living co-stars, because they're not actually there. Or there is some kind of stand-in.
The great strength of something like Yoda in ESB and Jabba The Hutt in ROTJ is that they were there on-set and the actors and puppeteers could really work off each other. The performances were much more involving as a result.