I know I'm late to the party, but I've started a play-through of the original Bioshock. Damn, that's a fantastic game. When I'm done, I'm definitely going to play both of the System Shocks (that is assuming I can legally download System Shock from somewhere).
System Shock 2 can be legally downloaded for $10 from
Good Old Games. The original one can only be played on DOS, meaning that it's effectively legal to emulate it.
This link on what's as close as you'll get to an official System Shock fan forum packages the emulator with the game, so all you need to do is download, follow the instructions given when you start the game, and play.
Keep in mind, though, it's a 1994 FPS that was one of the first (if not THE first) to have full 3D environments, including looking up and down and even leaning like a modern tactical shooter. It's also got a lot of items and weapons (more than both BioShocks combined, probably), alternate ammo types, audio emails and logs, and interactive environments. All in an era when most computers didn't have a mouse. So even with the mouselook mod packaged with the game in the link I gave, it's extremely clunky. The mouselook mod doesn't even really make it a full FPS control scheme: it works by locking the cursor to the center of the screen and making it so that the mouse motions control the camera, so it works like a regular FPS most of the time until you pick up an item and need to Tab back to "inventory mode" (really the actual mode the game was played in) to put it in your inventory. Trying to play it without the mouselook mod basically requires relearning how to play computer games.
Also, you may notice a ridiculous amount of similarities with BioShock when you play System Shock 2. Along with the aforementioned audio logs, radio/email communication with someone guiding you, and alternate ammo types, you've got the ghosts retelling what occurred before you arrived, researching enemies to gain bonuses against them (though much more in depth, involving the right chemicals from storerooms around the game to research and requiring certain items and weapons to be researched before they can be used), a short hacking minigame that can be bypassed with a limited amount of automatic devices, vending machines that can be hacked and dispense both standard and unusual items side-by-side (like grenades and chips), a grenade launcher instead of throwable grenades, hackable turrets, security cameras that summon enemies if they see you for too long, and various psionic powers that require hypos to recharge. And Ken Levine's preference for messing with common video game tropes and playing on the player's expectations as part of the plot. Though really, everyone knows the plot twist by now.
That said, it's also much more detailed than BioShock in some manner. There's several different melee weapons with different properties, firearms degrade and can break (requiring maintenance tools or a repair skill to fix), it has a large RPG-style stat system that requires upgrading your stats to wield certain weapons or perform research and learn new psionic powers, and a grid inventory with limited space (upgradeable by increasing your Strength stat or taking a one-time boost from one of 4 upgrade machines in the game), and implants (basically like gene tonics in BioShock) have limited power and are disposable items.
One good tip: if you raise your Standard weapon skill to 6, you can use the assault rifle (there's on available from the first deck if you know the Medical armory code or hack it open). It takes the same ammo as the pistol, but fully automatic and with much higher damage. Since pistols are the most common firearm after the shotguns that many enemies use and you can take ammo from discarded guns, it makes the pistol obsolete and will probably become a primary firearm for the whole game.
