Bioshock 2, the highly anticipated sequel is coming out on Tuesday. In short, this game just has new stuff. I almost see it as a DLC.
Bioshock 2 will have new plasmids, enemies, maps, a multiplayer, and you will be a big daddy instead of a normal person. What do DLCs usually contain? New maps, enemies, and abilities. But hey, this is a really big and really awesome DLC, don't get me wrong.
Anyways here is the breakdown:
Singleplayer:
The singleplayer is the main attraction to the game. The original Bioshock contained an amazing plot (with many twists, but I wont spoil it) accompanied by beautiful graphics and sound. The underwater city and its graphics and sounds are what made the first game. It was a new, refreshing idea that was done, dare I say, perfectly. The one drawback to the new game's singleplayer is that the scenery and sound isn't new. Sure, there will be new areas, but the idea itself just isn't as spectacular; nonetheless, I still expect great things from the singleplayer. The new combat system lets you use plasmids and weapons at the same time, which I fear will make it a challenge to switch between weapons/plamids. The plasmids seem to be redone, and let you fire constantly rather than just once. The splicers are all jacked up with new plasmids of their own, new weapons, and special "boss splicers" like in Left 4 Dead. (Rumor has it splicers can use everything you can). The splicers are also going to come in large groups, so that the idea of Big Daddies being really tough still exists (a damage reduction to the splicers also comes with this). So far the only released boss splicer is much like the tank from Left 4 Dead; he is huge, strong, and kinda difficult. Overall, despite the lack of new scenery, this game will be amazing.
Multiplayer:
The multiplayer is either a hit or a miss, no in between. They are taking a select group of plasmids and weapons and letting you use those, in the same way you would in singleplayer, in order to kill online opponents. What many critics, and even 2K themselves have said, is that the multiplayer wont be as fast as usual games; instead, the mutiplayer will be a little more tactical. You get to make three different classes with different weapons and plasmids that you can switch between when you die. Sound just like Modern War...something... hmmmm. Anyways, you have to use your perks... I mean plasmids... to be a little more tactical and perhaps freeze and enemy before shooting them like crazy. The problem is, gamers will either like this or hate this. Imagine how rage inducing it would be to be shooting someone, and then be frozen and unable to fight back. Overall, the mutiplayer sounds cool but it might just be too "different."

