IV is amazing. I'd recommend it. You don't need to have played the others first to understand it, the plot is sort of like The Legend of Zelda: similar tale repeating throughout the ages. There are some little references to the other games in there, but nothing that will leave you lost. It is extremely fast-paced and the difficulty is very well balanced. I find many RPGs to be mostly difficult in the beginning and the very end, but this one will keep you on your toes constantly. That said, it doesn't require extreme grinding between dungeons..

Music is great, graphics are awesome, and you are always meeting new and interesting playable characters.