During the story arc with Raditz they make it out as though it's the first time Piccolo and Goku team up. With Goku dying in the Raditz fight and not showing up again until Vegeta, it couldn't have happened after that fight. Where does it fit into the storyline before the Raditz fight?
This Wiki explains it pretty well:
Dead Zone is the only film that takes place after the end of Dragon Ball and before the beginning of Dragon Ball Z. The events of this movie can be placed into the series timeline between episodes "The End, The Beginning" of the Piccolo Jr. Saga and "The New Threat" of the Vegeta Saga.
All of the Dragon ball Z films Were fillers.
Except these movies:
Bardock: The Father of Goku
The History of Trunks
- wrath of the dragon (Very questionable)
Edit: In most cases it does not really matter, because the information is not synchronized with the series itself.