Basically if you're a popular marvel character you will get your run in the avengers.
which is ridiculously stupid.
I liked the avengers better when they were a bunch of rejects. that way i could laugh at hawkeye's silly purple and pink outfit.
Seriously the Avengers are everything wrong with Marvel. Street level heroes (spidey, wolvie) teamed up with Cosmic entities (Thor, SS, Sentry) to take on street level villains or evil cosmic entities (thanos, galactus) with no consistent power levels and a million plot holes.