I got my hands on a copy of BioShock 2 yesterday. When I got home I threw down my bag and entered the world of Rapture. Now, the intro for BioShock was awesome. The plane crash and the lighthouse in the middle of the ocean gave you that sense of discovery and awe. I didn't know what to expect then.
BioShock 2's beginning was a bit shock, but not awe. It was interesting to see that the Big Daddy you played was made to kill himself, and that some how was able to survive a gunshot to the head. It was also cool to see a flashback of Rapture before its end. But other than that I wasn't interested in wandering around Rapture like I was before, until I was introduced to the ability to explore Rapture in a new way.
When you meet the Big Sister for the first time she breaks through a rooms glass wall and lets all of the water fill the room introducing a new exploration dynamic that BioShock lacked. I could now walk in the ocean water freely without dying. I could explore new parts of Rapture with my Big Daddy suit that I couldn't before playing as Jack. When I walked out into the ocean I looked up to finally feel that I was at the bottom of Rapture.
In BioShock I always felt that I was moving forwards and backwards never up or down. You have this enormus city and all I could do was move vertically. I'm hoping with this new exploration mechanic, that they allow us to move upwards in Rapture, maybe at the top of one of the tall sky scrapers.