The best team would be:

RIKKU (ffx): Healer with her use ability, attacker with her mix ability
AURON (ffx) great attack power
RYDIA (ffiv) Meteo and summons. enough said
BUTZ as bluemage (ffv) Blue magic like mighty guard, white wind, lvl 2old, lvl 3 flare, lvl 5death, mind blast etc..

Think about that team. EXTREMELY GOOD