All throughout my childhood it was Spidey. I dunno, just the prevalence of Spidey marketing over every other character, probably. You didn't see many Silver Surfer coloring books, you know? Really as a kid I expressed interest in Spidey, Batman, and the X-Men, due to the cartoons. But as I grew up and started appreciating comics themselves, it became clear to me that Spidey just did not have as many quality stories as some other heroes. First I latched onto Batman, because I've always liked him due to the cartoons, and it was apparent that he had a lot of good stories. Then I read Miller's DD stuff, and then yoda and CTOAN and Lackey got me into Bendis' DD...so I can firmly say that my favorite character is Daredevil. Still, it's hard to get over old crushes. I still love you Spidey Man
I didn't really determine it. I just found myself really, really enjoying Thor's comics, concepts, and themes more than any other character's and figured, "I guess Thor is pretty much my favorite character at this point."
Before Thor, it was Spider-Man. That was mostly due to my dad's liking Spider-Man so much. (I also had a soft spot for Green Lantern because of my dad. Thankfully, Johns showed me what a truly terrible character Hal is and I overcame that.)
Mine were initially determined by what I saw on TV as a child. DC had it on lock-down at the time with Batman & Robin (Adam West) and Wonder Woman (Lynda Carter). The former had me tying blankets around my neck and jumping off couches like an freakin idiot.
Then came along Chris Reeve's "Superman" and Lee Major's "The Seven Million Dollar Man". These characters had me blowing on things thinking I could freeze them and sticking my fingers in light sockets to see if I could run faster (true stories all). I wasn't allowed to watch "The Incredible Hulk".
Then I grew up and discovered the world of Marvel. The X-Men, The Fantastic Four, Power Pack...these teams seemed more *real* than the passe "Super Friends" cartoon. I was totally caught up in "Secret Wars"...had never read anything like it. And having a black mother and white father I was searching to "identify" with some of these heroes so characters like Storm, Bishop, Black Panther and Luke Cage helped me find a balance I couldn't find in DC's comics. Since my family was mixed culturally, it was great seeing heroes of every color and background fighting side-by-side.
And now I'm here with you guys...31 years old and still believing.
*falls backward off plank hoping someone catches my ass*