No, The games aren't the -same- thing. Actually from the 1st to the 3rd there's quite a big differance. Also, what makes a game differnet if not for,
"gameplay, new story, new place, slightly better graphics, but is overall the same game."
If you take away those elements than in general all games are the same damn thing.
POP3 starts off with the prince returning to babylon inorder, while it's under siege.
You'll enjoy who's attacking babylon (only if you've played the other games.) I'm maybe 6 hours into it. I'll let you know more later.