5. Chocobo Treasure Hunting (FFIX)

A fun minigame leading into a sidequest that feels really rewarding? Sign me up.

4. Henne Mines (FFXII)

What can I say, I'm a sucker for tough optional areas and this one certainly fits the bill. It was a toss-up between this one and the Nabreus Deadlands + Necrohol of Nabudis optional area, but in the end I had to go with the one that feels the most oppressive. That music is one of the most ominous things I've ever heard.

3. Catching Monsters (FFX)

Somehow this one just worked so well for me. It's probably the constant, continuous progress you make coupled with the fact that the rewards are extravagant and awesome. It was actually fun going back to earlier areas just to catch 10 of every fiend, and managing to make pointless grinding (especially on fiends you can long since overkill ten times over) turn into that is quite an accomplishment.

2. Chocobo Breeding and Racing (FFVII)

Truth be told over all these repetitions the process has become a little tedious, but I still vividly remember how cool all of it was the first few times through. The whole sidequest just pulls you into its fluffy and lighthearted atmosphere as you get totally invested in making these giant chickens in different colors and have them race as fast as you can. It's glorious.

1. Via Infinito (FFX-2)

I've talked at length about this dungeon already, but I'll gladly do it again. It's by far the toughest challenge in any of the Final Fantasy games and becomes absolutely relentless in the final few levels. FFX-2 does have some powerful stuff in it that makes getting through this dungeon a lot easier, but chances are you'll still get a glimpse of how terrifying this place is if you take it head-on. This dungeon is one of the reasons I started thinking more about what makes a fun challenge.

Honorable mention to Creature Creator in X-2 HD, it probably would've taken #2, but I didn't want to have two entries from FFX-2 on the list.