Having grown up with Final Fantasy IV on SNES, I recently enjoyed playing through Final Fantasy III. For my own edification and those curious, I'd like to note some of the design similarities between the games, providing color on the evolution of the Final Fantasy franchise.
- Airships are a primary theme, both as transportation and cultural status.
- Final Fantasy 3 introduced the character class system in a big way, setting the stage for the classes used in FF4's story.
- Desch and Yang provide similar service to their respective stories: help the party for a while, followed by dramatic sacrifice.
- FF3 introduced the Toad and Mini status effects as first-class gameplay elements. Toad allows you to swim and Mini allows you to fit in tiny passages. While Mini, your attacks are useless but magic still works. These status effects remained in FF4, although vestigial. (I always wondered why "mini-mages" were so common in FF4. Without having played FF3, they didn't make sense.)
- FF3 introduced the Leviathan, Odin, Bahamut hierarchy.
- Eureka (FF3) paralleled the Lunar Subterrane (FF4). They're both extremely hard when you first enter, but they force the party to gain about ten levels. In addition, they contain several smaller bosses and a bunch of powerful equipment. Both provide a sense of progress and accomplishment, without feeling like grind.
- The last areas and bosses of both games are unusually difficult. They each took me multiple attempts to complete.
- In both final battles, previous allies provide "spiritual assistance", making it possible to defeat the overpowering final boss.
However incomplete this list, these are the similarities I noted. Final Fantasy 3 had not quite discovered the Final Fantasy "sauce", but it was an important step along the way.