yeah 4 was good because they kept to the story and most of the dialogue was unchanged, 3 was also well done on the ds. The environments were true to the originals. This however was much easier because they are on a graphical level of about the n64 if not a bit better. If they were to make a 7 remake for the ps3 they would have to include voice over, reanimation, remodeling, re-script, redone battle format, redone field and world map environments and everything from scratch. This leaves a lot of room open to cut corners or leave out certain details. Some areas of the game might be entirely changed and the world might could just be omitted entirely.
It would be great if they did it but I don't think it would ever happen, and I think the real reason is because they know how many people would be pissed if they didn't make it perfect and they don't really want to put the time and effort into making it perfect when they could just as easily charge the same $60 for a new game that keeps pushing the copy and paste dialogue and lack luster game play as we find in XIII. I like the idea of a remake just as much as the next guy but its the quality of the project that concerns me. Now if they remade seven with the same graphical quality as the 4 remake then it would probably come out very well but it would also probably be for a portable device and that kinda annoys me. Yeah its cool any everything to take your games with you, but IMO its more of a gimmick than anything really.
I think it will be done eventually, whether by the fans (I mean just look at the amazing things Team Avalanche are accomplishing), a future company, or Square Enix themselves. However, unless they are making it the most secretive gaming project ever and are already 90% complete with the game and plan on surprising everyone with the finished product. Then I think it won't happen for a very very long time. Probably not until the current tech is long obsolete. Which in truth is completely fine by me. I think the best way to play a FF7 remake would be in a virtual reality simulator anyhow :p
