Andrew Ryan is voiced by Armin Shimerman. You might remember him asQuark or Principal Snyder or Nefarious. It can be difficult to recognize him the first two times he is heard, though - Shimerman absolutely nails that cultured fifties style of phrasing in the Rapture introduction and the second time he speaks is through a PA system. But he is clearly recognizable after he begins communicating with the player over their portable radio and in the voice recordings.
Frank Fontaine after dropping his Atlas guise is voiced by The OtherIroh.
Dr. Steinman is voiced by Peter Francis James, who can be often be seen on one Law & Order show or another as a judge.
Naledi Atkins' voice actor also voiced another female pilot whose plane was downed, namely Captain "Deadly" Pelayo from Modern Warfare.
The "Lady Smith" splicers and Dr. Langford are voiced by the same actress, whom you might know better as Wanda and Timmy's mom in The Fairly OddParents. She's also taken over voicing Cruella de Vil, Maleficent, and Lady Tremaine in recent Disney works such as Kingdom Hearts.
Sander Cohen is voiced by T. Ryder Smith, who might be best remembered as the villainous Trickster from the 90s horror film Brainscan, but more recently has been the voice of Baron Underbheit on The Venture Bros..
Within the first game itself, it's clear — and a bit jarring — that they re-used Peach Wilkins' (unnamed) voice actor for one-off character Charlie.
In Bioshock 2 the spider splicer model named the "crawler" is voiced by Sasuke or Ben depending on which one you're more familiar with.
The Japanese voice actors are more easily identified as Toshiyuki Morikawa is the voice actor for Atlas, Andrew Ryan is Unshō Ishizuka, Bridget Tenabaum is Mie Sonozaki, and Kaori Shimizu voice the Little Sisters. In other words terms, Shaggia Frost wants Jack to kill Sergei Smirnov while Aplodia Neuro tries to save Signum and Lain Iwakura.
The original BioShock game underwent many, many changes from the time it was pitched to the final product. The original pitch still had the Zeerust idea; they wanted it to take place on land, however, in a series of interconnected controlled environment chambers created by 1940's Germany. The laboratories would be full of mysteriously dead human bodies, being overrun by strange, insectoid life forms called Gatherers, who collected genetic material and body parts, the Protectors for the Gatherers, and predatory Aggressors. These eventually developed into the Little Sisters, Big Daddies and Splicers, respectively, when the developers decided they wanted a more "human" angle. The concept art book for BioShock shows off some of these life-forms; particularly striking is one insectoid being half-fused into a human body using its arms and legs to walk and fire a pistol. Among other things promised was the ability to alter the controlled environment, such as raising the temperature in an area and giving yourself a plasmid that protected you from heat exhaustion.
According to the original pitch of the game, you would have played as Carlos Cuello, a "deprogrammer" asssigned to infiltrate a mysterious cult based on a remote island and "rescue" a wealthy heiress being held there. The game would have also included a much more in-depth weapon creation system, based on the superpower creation system in Freedom Force. Some of the weapons you could make included a triple-barelled automatic shotgun, a silenced railgun, magnetic grenades, a sniper rifle that shoots acid-coated bullets, and a chain lightning taser pistol.
One of the insectoids nearly made it to BioShock 2 - the concept art shows Splicers turning into things that made G-Virus mutants look cute.
The original game had Jack mutate more and more with plasmid use, and would make players decide if they wanted to become a hideous freak like the splicers to survive, or refuse, keeping their humanity at the cost of less safety. The final product encourages you to use more ADAM and EVE.
The weapon mods originally looked like they were cobbled together with random household junk MacGyver style, as a means to emphasize how Rapture was supposed to be a mostly weapons free society. Levine decided that the weapons ended up looking "dorky" and thus changed the mods as to still look hand modified but "by someone who knows what they're doing".
The sequel went through several huge shifts in storyline and themes during development; originally the Big Sister was intended as a single Big Bad or The Dragon, a former Little Sister incapable of adapting to life on the surface who had returned to Rapture to try and rebuild the city of her childhood, kidnapping girls to do so, with Tenenbaum returning to try and clean up her mess. This entire plot was more or less scrapped in exchange for a Perspective Flip with a religious collectivist villain in contrast to the first game's atheist Objectivist Big Bad.
At one point, the sequel was to have Soviet Russia invade Rapture, with the Soviet troops fighting splicers. They were meant to be much more intelligent than the batshit insane splicers, and would use efficient tactics (taking cover, hiding, flanking, et cetera). (It was even in some demos shown to reviewers.)
There were to be more survivors that had barricades themselves during the Splicer outbreak and were to assist the player, but this was during the "Big Sister is the primary villain" phase.
Also during said phase, Mark Meltzer was apparently supposed to play a bigger role in the story, even being the one who hired the main player (either a detective or a parent whose daughter had also gone missing) in the first place.
Subject Delta's armor used to be based off of old World War II bombers and would have been a lot more top-heavy and bulkier.
Sander Cohen was planned at one point to return in BioShock 2 as a "20-foot-tall Freudian monster bunny".
Some of the elements above (man infiltrating hidden area, singular Big Bad/The Dragon harassing you at every turn) are being recycled into BioShock Infinite, while the Russian soldier AI was utilized for the Splicers in BioShock 2.
During the early stages of BioShock 2, there was a giant squid boss that Delta was supposed to fight outside of Rapture.
The concept art displays many things that didn't make the cut of Infinite, such as a darker atmosphere more akin to Rapture and enemies that had damage from portal cuts and reality shifting.
Dionysus Park was originally conceived as an area of Rapture that was clean and not destroyed by all the fighting of the civil war. Delta was also supposed to get there by taking a scuba-diving trip through Fort Frolic, which had become completely flooded since Jack's visit in the first game.
Infinite also went through several development cycles. In the games early trailers, there are a lot of characters you never meet, places you never go, and powers you never get in the main game. One trailer notably takes place on a bridge that is seen frequently through the early portions of the game but never visited.