I saw a video on youtube with all of the changes between releases. In the earliest version (1977) Greedo shoots first, but misses. But it all doesn't raelly matter as Han was the one who survived...
If you look at the "Greedo shot first" footage, you can see Han's head was very poorly edited sideways. It looks like someone just clicking and dragging in photoshop.
I checked it again: https://www.youtube.com/watch?v=RNbzSH84mj0
(1977) Han shot first. Greedo didn't shoot at all.
(1997) Han shot second, head shifted like phoenixsenshi said, and Greedo shot first.
(Other) They shoot almost simultaneously.
He is done with this shit.
(1977) Han shot first. Greedo didn't shoot at all.
(1997) Han shot second, head shifted like phoenixsenshi said, and Greedo shot first.
(Other) They shoot almost simultaneously.