Zone of the Enders 2 is probably the best Giant Robot game ever made. Period.
Gameplay - It's quite a bit like how the first one was except this time it's way faster, way more solid, has more features, more moves, just more better in general. There's just a lot more fun to be had here. Most of the time you will be fighting and most of the time it will be lots of fun. The only complaint I have is that towards the end, after you've basically unlocked everything, the game just loses all difficulty. Graphics - Basically they revised the whole design the first ZOE had and made it into what a Giant Robot game should be: Anime like. The anime cutscenes are all well animated and they look great. There's a whole lot of cool new anime like effects In-Game this time around. Although, during some of the more graphic heavy or enemy heavy fights, the framerate can take a real hit. But hey, it was 2003 and this game looked outstanding for it's time.
Sound - The music in this game is amazing. The thing holding the sound back is the voice acting. Most of it is very sub par. The delivery of some lines in particular leave a lot to be desired and even some of the lines themselves are cheesy enough that it probably doesn't matter. But, they do a decent job and at least it's better than the first ZOE's.
Replay Value: This is not a long game unfortunately. Just when the story and the fun really starts to get amazing, you'll suddenly find yourself at the end already and wanting more. Probably, it will take you 7-8 hours to beat this game. Maybe 6 if your really skilled. It's a real shame that ZOE 2 ends so quickly. But, the single player game is ton's of fun and you'll probably find yourself wanting to go back through it just to unlock more stuff for multiplayer and all that. And speaking of which, the multiplayer is pretty standard and it's pretty fun for awhile.
Ultimately, this is what the first ZOE should have been. If you love Giant Robots and love Anime, I would definitely recommend ZOE 2 to you. It will pretty much blow your mind in more ways than one.