The actor's performance is lauded so consistently that the prosthetics really don't seem like a problem for most people. We're mostly not beyond the point where sci-fi aliens are basically humans, because they're played by humans and speak like humans. Whether it's make-up or motion capturing for CGI.

It takes huge efforts to move beyond that, like Rocky. I'm sure there are more, but probably not many - anyone got other examples?

G'Kar's prosthetics are actually shockingly malleable. The brow actually moves and the area around the mouth is soft enough for stuff like big grins.