DC or Marvel...

Don't get me wrong, I don't collect comic books and I'm not some major comic book geek, but I do love every comic book movie I've seen; X-Men, The Avengers Series, The Dark Knight, Hellboy, Watchman, etc... and I know enough about their origins to have the "DC or Marvel" conversation. My mother, apparently, doesn't. Imagine: me, my mam and one of my friends who's a total film buff;
Me and my mate: squeeing over Ledger's Joker and the funny scenes from Thor.
My Mam: blank look
Mate: DC or Marvel?
Me: Both!!
'Cause that's my stance on the matter.

And if anyone could tell me where to start reading for both continuities, 'cause they both never seem to start, just run endlessly into one another. Be a real help!! Phe xxxxx