My first instinct: A TPS in the universe of Valkyria Chronicles, borrowing mechanics from steampunk and the rocket suit from Vanquish.

Paper Mario (rpg)-> Sticker Star (action-adventure) ?

its not always for the best.

TTYD is still by far the best Paper Mario game, and them makeing it this non rpg sticker thingy has not worked well.

hmmm let me think.

How about a fully 3D Kirby? like Mario Odessey but with kirby?
Same with Ecco the Dolphin, I think that could work in 3D.

Grand Turismo that was a kart racer or Rally type racer? :)

I would like to see a the order 1886 rpg. It didn't work as a shooter, but the world seems interesting enough for a RPG.

A metroidvania Tomb Raider spinoff could be interesting, but it'll never happen because it's not a good idea from a financial standpoint.

I'd like to see a Megami Tensei horror game, retaining the RPG elements but just creating an atmosphere in that vein.

I would like to see a mainline Mario game that's a shooter, where Mario shoots up terrorists.

Zelda as more story driven and cinematic, with smaller environments and less battles. It would be nice to see if they could make it work.

It would be hated, but still it would be interesting.

That'd be interesting I guess.

I'm a firm believer in not changing what isn't broken. Even when it goes right, it usually doesn't exceed the former game. I'll take Mario Bros. 3 over SM 64 any day of the week. The same goes for Super Metroid over Metroid Prime.

The only game I can think of that I felt a change made it better was GTA.

Well i'd love to see a Castlevania game in the veins of Dark Souls. I think that'd be the perfect gameplay to translate it's 2D elements to 3D. Sometimes when playing DS/Bloodborne, it's overall atmosphere, exploration and combat reminds me the way my brain filled the gaps of the classic Castlevanias as a kid. (mainly 1, 2, 3 on the NES and Super Castlevania IV on the Snes). So yeah, a souls-like Castlevania, just think about it...

Also i'd love a TPS Megaman X, in the veins of a MGS: Peace Walker meets Megaman Legends. Missions with different objects, a lot of areas to explore, maverick hunter's base management, find and recruit reploids, rpg elements, etc. It'd be hard to make such idea work, let alone make profit of it, but if done right, i think it would be dope.