This is the rare RPG shooter that gets everything right. The graphics are wonderful, the environment is memorable and the shooting includes strategic aspects that add a lot of depth and make each encounter memorable. There are also some light RPG elements here in the form of plasmids that alter your characters abilities. It's no Baldur's Gate but it does feed into my compulsive need to collect and see everything a game has to offer.
The real star here is the environment and story. The game takes place in an underwater utopian world that's essentially gone to rot. There are tons of unique enemies and individual environments and the story is effective at keeping you invested in the ultimate outcome.
Some of the Ayn Randish references would be distracting if the gameplay wasn't so bloody fantastic. Overall, this is as close to a modern masterpiece of gaming that one can find.