Ogre Battle.
I know everyone seems to love Final Fantasy Tactics to death, but I dare say FFT killed off the Ogre Battle franchise. There was so much more I wanted to know about the Ogre Battle world, and would have loved to see a modern version of Ogre Battle. This includes the SNES & N64 gameplay as well as the tactics variants. The designs, the music, the story... Ogre Battle 64 is my favorite game of all time. It would be awesome to see a "modern" Ogre Battle 64, but I guess that will never happen...
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Other games I would like to see return is Grandia (I only played the second, but I loved the battle system) and Skies of Arcadia. Granted, Skies of Arcadia can be considered a one off since one explores the entire world, but if Bravely Default can get a sequel, maybe Skies can do the same thing.
I would also say the Command and Conquer franchise, but aspiring modders and fans seem to have those bases covered. I don't think I can trust the big companies to do the games justice after EA screwed everything up.
Warcraft RTS, specifically Warcraft IV. Let Warcraft IV continue where Warcraft III left off and leave the WoW and expanded universe stuff out of it. Then again, Blizzard's stories have been getting weaker over the past few years, not to mention the over reliance on lore outside of the games themselves to explain events. Still, I'll watch Pixar's Blizzard's Overwatch shorts.
Advance Wars. I would like to see its glorious return. While the Days of Ruin artstyle I had to adapt to, the gameplay and editor was amazing. I want to go back being a kid and messing around in the editor, making up little stories on why these conflicts take place and stuff...