In your side view, it looks like your character is slanting or leaning back. I'd suggest reworking that pose. I think his feet should be placed further back. Also, the side view has a slight angle to the eyebrows so it looks like he's a bit mad. In the front view, his eyebrows are neutral. Maybe that's why you think it doesn't look like the same person. The side view head also seems to be one pixel smaller than the other heads so that might be another thing to look at. I think adding a pixel or something for a nose on the front view (since you have one on the side view) might help in making the character look the same when facing any direction.