The first one is simply awful, it's just Elizabeth on a generic sky background. It ignores all the games gorgeous locals and it's just using a pretty girl (and breasts) to sell the game.
The second one is far more interesting, it's an unique image with a great art, but it doesn't sell the game all that well.
The third one is...alright, I suppose. Booker and Elizabeth are way to realistic to the game's aesthetics. And the background is also a bit plain. If the two had that slightly exaggerated look like the rest of the game and the background was Columbia it would be good cover.
The forth one is really freaking original and interesting, but I think it's more interesting than good, but that's just my opinion.
The fifth one is pretty much the same thing as the third one, except for a different angle. It's a bit better than the third one.
The sixth is probably the strongest of them. Great art and perfectly represents the game, but a good background could make the image far better.