Look at this. :)
Nintendo = NES
Super Nintendo = SNES
Playstation = PS
Game Name: Final Fantasy: Era of Generations
Company: (Hopefully, Square Enix would make this)
Description: A powerful monster have been released, and is plotting to destroy time. For the first time ever, heroes and villains team up to defeat this mysterious monster. Play as heroes and villians from Final Fantasy 1-9, and help them defeat this beast.
Main Characters:
Warrior of Light - from Final Fantasy I(NES)
Firion - fom Final Fantasy II(NES)
Onion Knight - from Final Fantasy III(NES)
Cecil - from Final Fantasy IV(SNES)
Bartz - from Final Fantasy V(SNES)
Terra - from Final Fantasy VI(SNES)
Cloud - from Final Fantasy VII(PS)
Squall - from Final Fantasy VIII(PS)
Zidane - from Final Fantasy IX(PS)
Garland - from Final Fantasy I(NES)
The Emperor - from Final Fantasy II(NES)
Cloud of Darkness - from Final Fantasy III(NES)
Golbez - from Final Fantasy IV(SNES)
Exdeath - from Final Fantasy V(SNES)
Kefka - from Final Fantasy VI(SNES)
Sephiroth - from Final Fantasy VII(PS)
Ultimecia - from Final Fantasy VIII(PS)
Kuja - from Final Fantasy IX(PS)
Gameplay: The gameplay will be similar to I - IX, but there will be three main regions of the world map: Nintendo Era, Super Nintendo Era, and Playstation Era. Each Era have a set amount of towns, dungeons, cities, and other familiar places you must visit to progress through the story. As you complete each parts of time, you will unlock more areas. For example, when you complete the Final Fantasy I section, you will unlock the Final Fantasy II section,. Once you complete that, the next in the series will unlock. Eventually, you will get to the next Era of time, which would be the Super Nintendo Era if you completed the Final Fantasy III section. Boss battles will be both old and new, as well as completely new enemies appearing.
System: (Hopefully for both the Xbox 360 and the Playstation 3)
It's not real, but it would be a good idea. I don't know if they are doing something similar to this though.