Yeah...But the game is a FANTASY world...It's not the middle ages in our time, obviously...There's magic, monsters, and other bizzare crap going on. I think the original names fit it just fine. I don't see how you can argue the setting as not fitting with their names...The setting is a fantastic landscape where anybody can have any name...or hair color! 
It just seems like you shouldn't have to change the name that the creator gave them...I mean, it's like adopting a kid and saying, nope, sorry kiddo, don't like the name your parents gave you, I'm changing it. Tough shit.
But that is the very point: in a fantasy world, especially, one must maintain internal consistancy and feel. A name like Jacky - admittedly Maou less so, but even it to some degree - breaks this. You see, as designed, the game is starkly western middle-ages. The castle is western in design style. The weaponry and armour, save for Crono, are likewise. Zeal, for its part, has more of a middle-eastern feel. To thrown in names of another tradition is, to someone as me that considers names carefully, extremely incongruous and grating. Jacky alone would totally break the feel and mood of Zeal. Even Doreen, which was kept, comes perilously close to doing this. They sound far too colloquial, and one cannot take seriously the feel of it being ancient.
The thing with fantasy is, there are stern rules one must obey. It may not seem like it, and it may appear as though anything goes in fantasy, but that is not the case. Too often things are destroyed by simple going too strange, just because it can. Think of what is considered the penultimate, or at least the originator of, modern fantasy, Lord of the Rings. It is inherently based in our world, with our rules. It follows some strict lines, and does not stray greatly from the real. This follows in names especially. The people from the regions have purposed names. In Rohan they have names in the tongue of the Rohirrim (pardon me, Tolkien claims to actually have translated the names from original Rohirrim into Old English for the sake of the story, but has kept the meanings the same. Regardless, the feel is kept), names such as Eowen, Theoden, Thengel, and Eorl. Amongst the Elves, and those of Gondor, names in lower Sindarin Elven, or higher Quenya, are common, such as Elrond, Glorfindel, Denethor, Faramir, and have their own sound. Names from the East are more eastern: such as Khamul, shadow of the East, the second of the Nine ringwraiths. Amongst Hobbits, they have their own unique sound, though this is rendered in English for feeling - again a purposed thing, for who would wish Sam to be called by his real name Banazir*? That is Hobbitish, after all, and you notice more in line with a name like Merry's, Meriadoc. Then there is the Black Speech, with lines such as Ash Nazg Krimpatul. Or Adunaic, which is a little harsher, too, of which I think Tar-Kalion stems (though it might be Ar-Pharazon; one is Elvish, the other Adunaic, but Adunaic comes from Elvish.) Now, the point in all of this is to illustrate that it is paramount that the names, especially in a fantasy setting, continue the feel of the region. Jacky, or Jeal for Zeal, does not do this. It may in Japanese, but it sounds, at least to my western ears, immature. That is not to say that there were not silly-sounding ancient names (Sulilupiamus, anyone?) but for the most part, they sounded grander (Marduk, Ekbatana, Uruk, Nippur, Lagash, Ishtar, Tiamat, and so forth.) Words and names in stories are meant to evoke a feel in the audience. If the traditions change, as they do from East to West, so do the connections with words and sounds. Thus it is paramount to change it to maintain the desired feel, which is the important factor.
*This, and the names from Rohan, serve to exemplify my opinion the best. Tolkien 'changed' these names - or, spoke of them as having been changed - for the sake of the audience. We could have easily done with Banazir, after all, or likely with any of the actual Rohirrim names. But he used changed version - changed when it was not really neccessary, if one thinks about it. It is one of the things that must be considered in fantasy writing as in no other. Moreover, if the names were not changed... would you like them to call Sauron 'Thu' all the time? Or yet older, Tivaldo Lord of Cats? Those are not just other versions of the name (like Thauron is). He changed these to fit the feel of his langage and tales, and the like. A similar thing might be said with Chrono Trigger. Some names may have a lot of meaning to an Eastern audience (say, Maou), but mean nothing to a Western one. Thus changing it, to retain its impact, is in order - Magus is the best example of this, actually, as the names mean the same thing. In many of the other examples, say Jeal to Zeal, Jacky to Janus, the translator actually made the game deeper and more thoughtful in his changes, and that is near always for the better. Personally, it would actually turn me off a game to have characters named Maou and Kaeru, but that might well be just me.
