I've got all the Marvel Adventures, and I've read (or in some cases, skimmed) most of them. The best stories were the first few issues of Fantastic Four. Issue 0-3, I think it was, had single issue stories that seemed to take place in the 616. But, now that title kind of sucks. Most of them are for small kids who you'd like to introduce Marvel to. The villians are treated as if the hero has met them for the first time. And, sometimes, the different books have used the same villian, like Fin Fang Foom in Fantastic Four and recently in Spider-Man.
Avengers is one of the best you can buy...although, the last issue of Spider-Man was decent. Peter David wrote that one, and it has some nice comedic elements between Gwen Stacy and Fin Fang Foom. But, if you want a decent Spidey story about Peter in his high school years, Spider-Man Loves Mary Jane is so far superior than Marvel Adventures Spider-Man.
Overall, unless you are a Marvel completist like myself, avoid these books. Marvel would be better served having one-shot stories that take place in the 616.