I really liked the maps of Final Fantasy VII and Final Fantasy IX as well. I've spent countless hours exploring both. I think they both show great variety, but overall I think I like IX's a bit more than VII's, even though I have probably spent more time in the world of VII than in Gaia.
Gaia just looks cooler, it even has mist (I know it's story related, but still) and other stuff! Plus, it just looks appealing and overall amazing.