Mystic Quest is by far the worst FF game I've played. It was painfully easy and its cast of characters had about as much depth as a piece of rice paper. Of the numbered titles, FFII takes my number one spot for worst game. It seemed as if the game wanted you to spend the vast majority of your time level grinding so your party wouldn't die at every encounter. Leveling magic became particularly annoying, especially spells like Flare and Ultima, which do about as much damage as any other spell unless for some unholy reason you actually decided to max them out to level 17. I will give FFII credit for giving me at least one good laugh. It's hard not to laugh at a line like:

"Guy speak Beaver!"