For me, Black Mask seems great. Joker, Harley Quinn, Two-Face, and Penguin also all seem really good, but who else would you want?
 Deathstroke (many people might know him as Slade) would be nice for me.

Clayface.
Deathstroke isn't a Batman villain, is he? I thought he was a general villain to the Justice League and Teen Titans.

I don't really know. Maybe one or two new ones, but I felt that all of the villains in Arkham kind of made the game's villains seem interchangeable except for The Joker. Maybe a more concentrated group of evil-er villains than the whole lot of them. But I completely understand about the fact that they need a lot, seeing as it's one of the game's selling points.

Catwoman, Pfeiffer style

They don't need alot, though. They just need to use the specific villains that have a lot of disposable minions.

mr. freeze- I think a big ice level would be fun. 
 
scarface- i want to see batman fight a puppet
 
madhatter- funny character who could replace scarecrow as the psychological/ fantastical villain

Joker-dorf

Two-Face, Catwoman, Mad Hatter, Mr. Freeze.

" They don't need alot, though. They just need to use the specific villains that have a lot of disposable minions. "

" Clayface. Deathstroke isn't a Batman villain, is he? I thought he was a general villain to the Justice League and Teen Titans. "

" mr. freeze- I think a big ice level would be fun.   scarface- i want to see batman fight a puppet  madhatter- funny character who could replace scarecrow as the psychological/ fantastical villain "   

 far in the distance "hohoho"....

i want to see joker, harley, scarecrow, penguin, 2 face, riddler, and mr freeze 
I DONT WANT POISON IVY IN THIS FUCKING GAME!

and i want robin and alfred to play a part as well

Catwomen, Two-Face, Penguin. Man-Bat for shits and giggles.

" and i want robin and alfred to play a part as well "

wanna see two face

Hush, Two Face and Deathstroke.

Two Face, Firefly, Mr. Freeze, Catwoman. 
 
Lets do it, Rocksteady!

I definitely would like to see Mr. Freeze and Penguin. I'll probably only see one of them though.

Mr. Freeze, an ice area would be cool.
Two-Face, why not?
Scarecrow, actually fight him.

Two face and Clayface

" Mr. Freeze, an ice area would be cool. "

Did you see the trailer breakdown on Gametrailers yet (link)?  Looks like Catwoman, Penguin, Two-Face and Black Mask are all strongly suggested in addition to the obvious Joker and Harley appearance.

Hush one of batman's greatest enemies 

Two-Face and Cat Women!

D.A.V.E. and Everywhere Man sound pretty ridiculous.  No wait, Man-Bat!
 
Batman appears to have some really terrible villains.

no idea. i'll just wait for Rocksteady to rock my world

I do agree with the Clayface. He could have been used real good in the first AA game. But why not bring him back for AA2. They just need a short little description on how he broke out of Arkham Asylum and got to Gotham. I do agree that the Ventriloquist is needed because Scareface is seen without him in the first AA game. Why not put the two together for the upcoming game. Only thing that has got me wondering is what doll the Ventriloquist will use. I'm taking it that he has more than 1 Scareface puppet. Remember the last scene we saw Scarface is was when you went into the room behind the visiting center, beat the Titans and then saw Joker throw Scareface on the ground. So how connected is the Ventriloquist to his puppet that we saw on Arkham. Is he brave enough to make a journey back to the Asylum and rescue it? 
 
*Mr. Freeze, I'm sure will be in AA2. Remember he was mentioned RECENTLY ESCAPED in Dr. Young's notes. With him being in the game I'm pretty sure he will be out trying to capture Dr. Evers so that he can restore the life of his long lost Victoria as seen in Batman Vengeance and the cartoons. His lab was always located out in that facility on the water. So we may get to use either the Bat-Submarine or the Batwing for multi-purposes in the game. 
 
*Bat-Mite, may be kind of interesting to have in the game. A lot of people don't know who he is. He was mentioned in the comics randomly when Batman's equipment would start 
malfunctioning for weird reasons. I'm thinking it would be interesting for Batman to be on a mission for the controls in his Batwing start acting weird and causing him confusion. And on the intercom inside the Batwing, you would hear a little sneaky voice saying "HAHAHAH, Batman. Lets see you get your way out of this one".
 
*Hush/Dr. T. Elliot is a very good for the story. If FireFly and Mr. Freeze are in the game, then he would be good to put in the story. Remember, it still has not been explained on how Mr. Freeze broke out in Dr. Young's notes. And if remember correctly, when you scan the schedule board inside the X-Ray room, it's obvious that Arkham staff have not discovered Dr. Elliot's true identity. When you come to think of it, Dr. Elliot could have easily let Mr. Freeze out of his cell. Fire Fly's fire pack is also seen inside of Arkham. So maybe they could have Dr. Elliot sneak Fire Fly his fire pack. Either way Hush/Dr. T. Elliot is a good person to tie into the story.
 
*Scarecrow I'm sure will be in AA2. If (Black Mask) is in there, then Scarecrow should work with him. Scarecrow did some work with Black Mask when Two-Face was chased out of Gotham and Black Mask resumed his title as the ruler of the FALSE FACERS society. Scarecrow also worked with Black Mask along side with Penguin and Clayface. So hopefully they will tie him in with the story.
 
*Ras Al Gu may also be mentioned. We all know him as the man that has lived for over 100 years. And when you beat the AA game, his body is no longer to be found where you first saw him. So that means members of the League of Shadows came back to rescue him.