Enemy skill in FFVII is broken like others have said. But I always use it.

I love Quina for sentimental reasons, though his/her blue magic rocks as well. Frog Drop + Auto Life = Invincible.

Strago is good, but other characters in FFVI are much better. Similar with the FFV Blue Mage. Quistis and Kimahri are just ok.

My favorite though is the FFXI BLU. The best job in FFXI simply because it can perform any role. True, it can't outperform the specialists at those roles but I feel that makes it all the more interesting. I absolutely loved my bag of tricks and being able to pop out a needed spell for the situation when we didn't have enough of some other job. They also looked badass in their artifact armor.

Blue Mage is my favorite FF job. I hope they add it to FFXIV eventually and also every other FF game with the job system.