I won't bother to review Final Fantasy and Final Fantasy II on iPhone in terms of the content of the games. Chances are, you've encountered at least the first Final Fantasy, or at the very least you have an idea of the kind of early turn-based RPG it is. (Final Fantasy II, which never made it outside of Japan until 2002, is a bit of a different story. It's old-school, but also really weird.) The gameplay is pure NES vintage, the stories are as barebones as ever, and the graphics are identical to the recent PSP remakes.
What is important to review for the iPhone port of any console game is the interface. And Final Fantasy is the rare console game that can make the transition to an iPhone control scheme intact. Not only that, the new interface is actually pleasant to interact with.
When walking around, you're left to the dreaded virtual D-pad, but you can only ever move in four directions in Final Fantasy anyway, and it's not like trudging through a town requires precise, twitchy movements. In battle, however, the interface has been completely replaced by a new icon-based layout that feels intuitive and streamlined. You simply touch the icon for your action (fight, magic, item, flee), touch the target, and you're done. The equipment and item menus are also optimized for the iPhone. It's simple to heal your whole team, or scroll through each team member individually to equip new weapons.
At $8.99 each, if you've already got Final FantasyI or II in some form -- especially on a handheld -- there's basically no reason to buy them again just to have them on a phone. But if you don't have them, or want the most convenient versions possible, these work just fine. It's surprising how well early RPGs transition to pick-up-and-play experiences. You can level up a bit whenever you have a free moment, close the app, and then resume the next time you have five minutes.
One word of warning, however: Final Fantasy crashed on me once. It may have been the software, or it may have been a quirk with my phone. In any case, it happened but once, and you should save frequently anyway.