I just wanna say, all these favourites are when the characters are done well...

DC Heroes: Superman, Green Lantern (just love the concept behind it), Green Arrow, Booster Gold (LOVE Bootster Gold), and totally because of the Tv show the Flash.

DC Villains: I love the simplicity of the Reverse Flash , Lex Luthor (specifically the way Grant Morrison writes him), the Joker (when done right :P ) and Sinestro.

Marvel Heroes: Captain America, Charles Xavier, Cyclops (I LOVE Cyclops, someone let me write this guy sometime), Thor, Dr Strange, Fantastic Four & the Inhumans

Marvel Villains: Dr Doom (what a surprise), Namor, Magneto, Galactus