In every Final Fantasy except IX I use them often. Only certain characters can revive others so I use phoenix downs a lot in all of them and tents if they're there. It's also hard for some characters to heal others so potions are a desperate source for my attack heavy characters. In most FFs I try and assign types of jobs for all my characters. To me it would seem weird for Vincent, Cloud, or Red XIII to be healers so I don't give them the cure materia at all and if I have a party with those three well I have to rely on items. Also in that game I remember there were flying enemies that only long range weapons and magic could hit it, so I used bombs in those situations because I didn't teach everyone good offensive magic at the time.

I guess it's the same for me with VIII too.

In X Rikku's Al Bhed potions were really handy when tyou first got access to them and still in some situations. Plus in order for her to deal good damage she needs to use her special items to attack. I love Hi-Potions in that game.

XII I can't really remember. I think I used ethers a lot but outside of battle if I could, and I had auto phoenix down useage for my non white mage/sage characters. Speaking of jobs. XII would've been a even cooler if they had a convenient job system.
In IV and VI, it's mostly elixirs, ethers, and phoenix downs.