Assassin's Creed II fixes everything wrong with the original, and it's fantastic!
Presentation: The story starts slow but is meant to be so you know what's going on, otherwise you would just get lost. The menus haven't changed except that there are now shops and you have to buy them.
Gameplay: Now with assassinations while hanging from a ledge, the game plays a lot more stealth-based. It's a lot more fun and allows you to plot. The addition of notoriety is sometimes annoying but realism is nice.
Graphics: It's great looking but not particularly astonishing.
Sound: The voice acting was obviously treated as one of the more important part of this project and the reset of the sound is great from music to effects.
Lasting Appeal: Trophies and collectibles, that's it but it will still keep you going even though the end of the game screws with your head.