Comic book characters have been adapted from panels to movies, tv shows, video games, etc. Based on the comics you are familiar with, what portrayal adapted the charcter the best? If possible, use comic book issues in reference.
I feel that Henry Cavill is physically the most accurate portrayal of Superman, and Ben Affleck the best for Batman. Gal Gadot did an amazing job as Wonder Woman, and Margot Robbie was equally excellent as Harley Quinn. But Matt Ryan IS John Constantine - it’s like the character was created with him in mind! And I honestly can’t see anyone else doing the part justice after Matt!
I agree with Ben Affleck for live action and Matt Ryan has played the best Constantine, but I prefer Keri Russell’s Wonder Woman more than Gal which may be due to the writing, but the 2009 Wonder Woman matched the comic story more, despite a more accurate character portrayal in Gal. Also, this is majority opinion, but I think Christopher Reeve is Superman from the comics. I have not read any comics on Constantine nor Harley Quinn, so my judgment is somewhat naive, but I am relying on research for portrayals.