Rapture is exactly similar to d previous game,so are the enemies n weapons n plasmids,what's different is the Big-daddy
Story is really the only element which saves the day,because combat is too repetitive(and super-imposed if u have finished the 1st one just prior to playing it)!! Playing as The Big Daddy(Delta,one of the oldest models) may certainly seem odd at first,but as the plot reveals,u'll find it a necessity on developer's side.Plot is pretty much similar to Bioshock-U were betrayed,now given another chance to redeem yourself and all,but the way it opens up is pretty interesting!!
Environment is similar as that before(Rapture),but still pretty decent.Graphics are Ok for a game dated 2010
Combat is basically similar to Bioshock,u have plasmids on your left hand,and weapons in your right hand.Leaving a few plasmids and some tonics(that modify passive abilities),almost everything is similar,except for a drill as a melee weapon,and a few new guns.ADAM is again there,and there's plenty of it to buy out almost everything.Enemies are similar(weird looking psychos,and other Big Daddies),except for Brutes(jerks) and Big Sisters(most difficult,even compared to the bosses),and some cult-survivors(have plasmids).Bosses are very few(2-3) and pretty easy to kill!!
Overall if u are a die-hard fan of Bioshock or u loved that game,it's worth playing,,but if u hated the former,don't bother yourself with this,