Marvel, for the fact it has the X-Men, one of the most powerful forces in Marvel and mutants like Jean Gray (especially as the Phoenix, and later White Crown Phoenix).
There are also the children of Reed Richards and Susan Storm, Franklin Richards and Valeria Richards. Franklin Benjamin Richards has the power to warp reality on a cosmic scale, and is an Omega-level mutant. Valeria Richards is more complex and can't be aptly described here, check Wikipedia if you want to know more on her, but she is impressive with just her superhuman intellect.
I never got much into comics, in fact I bought my first graphic novel fairly recently, which is actually a compilation of an old marvel series. I really enjoyed the marvel based TV shows though, spiderman, xmen and the like. And my friend and classmate basically read me every marvel comic from memory, introduced me to Marvel Overpower Card game, and basically assimilated me into the world of marvel.
DC is ok. Superman is home grown and the poster boy of superheroes. And Batman is the poster boy for "dark" superheroes.
Spider man (over at marvel) is the poster boy from adolescent superheroes, and The X-men are poster people for... Well superhero "freaks of nature." I recently started buying and reading "Onslaught: the complete epic." and while it has mixed reviews, anyone from my generations would like it because it ended an era.
My vote, in the end, is Marvel.
I read Marvel and Marvel only back in the late 70's thru the 80's and early 90's. I finally quit collecting when it got so commercialized (I.e. The multiple covers, some already sealed in plastic, etc...). The storylines really got left behind.
Although I have not read a lot of DC I have read some and seen the movies. I always felt Marvel characters were more real. Instead of a millionaire being Batman you have a pimple faced, poor kid who is Spider-Man. Instead of the guy who can do anything and, for the most part, cannot be killed, like Super-man, you have Incredible Hulk who struggles with being a raging monster at night and a shy scientist in the day.
Marvel, in the 80's, just cannot be beat for stories that make you crave the next issue.
How does Marvel compare now with the 80s? I've looked at some really old stuff before and the stories were so boring in both DC and Marvel, I just don't know how you older guys were like enterained with that stuff.