Warrior of Light & Garland - Final Fantasy
Firionel & Emperor of Palamecia - Final Fantasy II
Onion Knight & Cloud of Darkness - Final Fantasy III
Cecil & Golbez - Final Fantasy IV
Bartz & Exdeath - Final Fantasy V
Terra & Kefka - Final Fantasy VI (OMGZ)
Cloud & Sephiroth - Final Fantasy VII
Squall & Ultimecia - Final Fantasy VIII
Zidane & Kuja - Final Fantasy IX
Tidus & Jecht - Final Fantasy X
(I think there will be more - fingers crossed for Rydia, Celes and Vivi =D)
While it's great to see Kefka in 3-D, I'm not sure the heroes vs. villains thing will work in his case. Cloud vs. Sephiroth, Cecil vs. Golbez, etc. will turn out well, but in FF VI it was more a case of The World vs. Kefka rather than Terra vs. Kefka.
Besides, he is in his human form, which isn't going to help when he's up against demi-gods and gods.
... but I s'pose this version of him is post-draining the espers and statues...