Hard to choose between Dragon Quest 8 and RE Revelations. DQ is probably the best game on an objective level, but it's a port, while RE Revelations did so much for the 3DS as a system, showed how console-quality and handheld-friendly design can coexist in a way that foreshadowed the Switch, and showed that Resident Evil was still relevant despite the dud of RE6.
Ended up going with RE.