It really depends on the context. xD

For reading the comics, I think Batman is my favourite.

Of all the live action movies, Captain America is probably my favourite.

In cartoons I again would choose Batman. Maybe Robin too? (Which one tho... That's a tough choice xD )

For tv series (live action) I would have to choose The Flash. Green Arrow comes in a close second though!!

Lol I can't decide on an ultimate favourite xD