I have more Batman comics and I have so many fond memories of the character that technically he's probably my favourite, and certainly the reason I got back into comics again.
BUT
I have always had fun when reading Superman, especially Alan Moore's exquisite Whatever Happened to the Man of Tomorrow? Which I consider par excellence for comic book writing, even when compared to Moore's other works.
I consider Wonder Woman to be brilliant in the right hands, it's just that all too often she's turned over into the hands of grubby misogynist gits.
Power Girl is absolutely rocking, at least in her latest series. She's one of those characters that's only known for one thing, so most casual readers dismiss her, but anyone who reads her knows she is far more, and even the writers now play on the ridiculous assertions of her character, which makes it both a fun read, because she has good writers, and weirdly elitist, because you know that you have risen above the crowd who refuse any comic that they have some misguided belief it's pandering to them. Sort of like people who likes Lisa Foiles because they don't automatically assume that boobs must mean someone is pandering to the geeks. In fact, screw it, from now on Lisa Foiles is Power Girl!
And of course, Tim Drake. I haven't read any Red Robin, (ran out of money for comics a while back) but in the Batman books he is easily my favourite character, above and beyond the Dark Knight himself, and his relationships with other characters show how he could very easily become a breakout new hero if handled right in the next few years.
And a final sympathy vote goes to Spoiler, or Stephanie Brown, the new Batgirl, who I think rocks, but has been more a little mistreated at the hands of various artists.
FINALLY
My all time favourite two characters, beyond any other character in the entire DC or Marvel multiverse:
The Question (as Renee Montoya) and Batwoman (as Kate Kane)
Anyone who's read Elegy and Five Books of Blood, or even just 52, should know why.