Bioshock isn't bad it's just shallow. If you want a challengeless, generic, circle strafing FPS, go get it right now. I'd say it's the best at what it does, it just doesn't really do a whole lot. The plot is nice, even if it suffers from having bugger all to do with the gameplay. Also, it has one of greatest plot twists ever, that unfortunately is let down by the game itself after the plot twist.
Bioshock is not brilliant but you could do a lot worse.