The Red Mage sprite is amazing. I remember when I first saw it (in my counterfeit NES clone — I was a small poor kid in Brazil) it made me so excited to play it.
My go-to party when playing the original Final Fantasy was Fighter, Monk, Red Mage, White Mage. I always liked that the Red Mage was something of a generalist; they could wield swords and use both protective and destructive magic. They weren't as good at any particular thing as a specialist class and lagged a bit in the endgame, but they provided some much-needed flexibility in the opening and middle game.
Yeah, they were great for most of the game. I usually lacked focus to get to endgame, so they were pretty good to me.