I think Rockstar are a cooler group of people, so it's most likely they won't sue for the similarity between Simpsons: Hit & Run and GTA III. Besides, Sega should realize that Road Rage was a bad game, so there's not much point in suing.

I think the Ghostbusters thing was a little different. I think that the film makers had previously tried to buy the song I Want a New Drug, but were turned down. But then the theme song was made and sounded exactly like it, so they sued.