Deadpool and Deathstroke were made by the same creator.
Deadpool actually has a personality where as...Deathstroke does not.
Rob Leifeld has written for Deathstroke. It was awful.
The Flash is generic by today's standards, but you have to remember that he's been around since the 30's. When he was first created, he WAS original.
Same for Mr.Freeze who, outside of his powers, also has an actual character arch.
What is Deathstroke's character arch? Has it ever been clearly defined? And this comes from someone who actually does like Deathstroke.
Characters I would like to see in Injustice: Power Girl, Black Canary, Ra's Al Ghul, Lex Luthor, Zatanna, The Question, Mr. Myxtplk.