A good adventure movie should be 100% watchable by the family on a wet Sunday afternoon, have some sort of macguffin as the plot element and an element of mystery to keep the audience guessing. Crucially they don't have to be 5* movies, just a fun ride.

For my money I would go with:

The Goonies

Indiana Jones Trilogy

Armor of God

National Treasure 1+2

Atlantis: The Lost Empire

The Neverending Story

Laputa

Inkheart

The Kid Who Would Be King

The Forbidden Kingdom

D&D: Honor Among Thieves (New Entry!)

The City of Ember

Night at the Museum

Willow