R2 didn't need to be in the prequel trilogy. That decision was just dumb nostalgia-baiting.

The Clone Wars

Original trilogy

Prequel trilogy

The Thrawn Trilogy, featuring the introduction of the iconic Luke/Mara/R2-D2 trio.

A tie between OT and Clone Wars, but he definitely has his moments in the prequels (especially RotS)

His Clone Wars appearances (and isolated episodes) are lowkey what got me obsessed with astromechs altogether since they made him a much more fun and clever character with his different arcs

I like him and everything, but especially the original trilogy.