Dragon Ball Series
These are the movies and OVAs I’d say should be watched in relation to the original anime:
OVA 1 — Bardock, The Father of Goku: An origin story about the father of Kakarrot and Raditz, touching on the final days of Planet Vegeta set before the original Dragon Ball, this story explores what flashbacks in the Namek Saga only touch on.
DBZ Movie 1 — The Dead Zone: Set between the original Dragon Ball and DBZ, this movie serves as the backstory for later series villain Garlic Jr., as well as touching on the backstory of Kami and the hidden potential lengths of Gohan.
OVA 2 — The History of Trunks: Set in the alternate future world of Trunks, this story explores what led to his first Super Saiyan transformation and decision to travel back in time for his mother and himself.
DBZ Movie 5 — Cooler’s Revenge: Set during the three years of training for the Androids, Goku and some of the gang deal with the older brother of Frieza as Cooler seeks vengeance for his family’s dishonor, as Goku is reminded just how necessary his Super Saiyan power is.
DBZ Movie 7 — Super Android 13: A feature that doesn’t work so well with the main story, but surprisingly could work as a story in the unseen “Timeline 4” where the main Androids were defeated with a remote, the three Super Saiyans rise one more time before Trunks must return to his grim future.
DBZ Movie 9 — Bojack Unbound: Following Trunks’ defeat of his future’s Androids and a trip to let his past friends know, Gohan and the gang reunite for a tournament, though the aftermath of Cell’s explosion on North Kai’s planer has opened the door for an all new intergalactic menace.
DBZ Movie 13 — Wrath of the Dragon: Only a year after the defeat of Kid Buu, the Z warriors meet an ancient warrior known as Tapion whom needs help to stop the largest beast that has ever threatened the Earth, a foe that will take the full power of Super Saiyan 3 Goku to bring down.
OVA 3 — Yo, Goku & His Friends Return: Now two years after Guy’s defeat, the story where everyone meets Vegeta’s brother and remnants of the Planet Trade Empire must be dealt with.
DBZ Movie 14 — Battle of Gods: A couple years later, Goku and everyone meet their most powerful adversary in Beerus, the God of Destruction whom Gohan, Gotenks, the increasing powers of Vegeta, and even Super Saiyan 3 Goku may not be enough to defeat.
OVA 5 — A Hero’s Legacy: A century after Goku departed the world and a short time before his descendant would battle Vegeta’s in GT episode 64, we see how Goku Jr. learns of his family’s legacy and the power of his Saiyan heritage