It's just as everyone else says it is: the best Batman game to date.
I generally like games that are easy to pickup and don't require a lot of button combinations to master. The button pushing learning curve was quick and painless for me. There is never a requirement for me to do any really complex combos.
The flow of this game is great, it really make me "feel" like I'm Batman (admittedly, I've always wanted to be Batman). It takes place in one night in Batmans life after returning the Joker to Arkham. The player takes on the roll of the Dark Knight as he follows clues, beats up henchmen and other supervillians and rescues hostages on his way to taking down the Clown Prince of Crime.
The game looks great, it's dark and moody. If Arkham was real, this is what it would/should look like. The characters look great, Batman looks great, he's got armour that makes sense. My only complaint is that the police and henchmen all look the same.
Voice acting is what does it for me. Kevin Conroy voices Batman, hell he IS the voice of Batman as far as I'm concerned. Add to this Mark Hamil as the Joker and I don't need to go further on this subject, perfect cast!