http://www.gamespot.com/ps2/rpg/kingdomheartsrechainofmemories/index.html
Well, maybe it's a great fanservice. Most gamers would likely move on to the next best thing, rather than replaying something with better graphics.
This is just the case otherwise there would be so many remakes. Would be easy for developers. Same story, same gameplay, better graphics and easy money.
In general FF7 is the best game they made. FF13 might not be as good as FF7 ever was. It's still a good game. They are talented and should make new IPs.