Yeah, I think that's the biggest stumbling block for bringing new readers into the big two- there's the sheer amount of material, and there are just so many interconnecting stories and retcons and spinoffs and reboots and whatnot that it makes your head spin. It's very daunting.
For a Marvel storyline that's mostly self-contained, I really recommend Ultimate Spider-Man. It's a reboot in an alternate universe where Peter's still in high school, and it stands alone for the most part. Invincible, the Umbrella Academy, Planetary, and Kabuki are also really good self-contained series.