Guardian Heroes for Sega Saturn. I know there was the GBA sequel, but it was terrible, and a very different style game.

Dirty Bomb

Cyberstadium Series: Basewars.

Sure, it was only 1 game, so maybe not a series, but as the name suggests, it was meant to be a series.

Tokyo Xtreme Racer

And thankfully, they just released a teaser for a new one so I guess my wish is going to be granted!

I'd really like to see another time-based drama similar to The Last Express. It had a lot of time-based events where you could run into particular passengers of the train in the hallways, and gained a strong sense of physical "presence" as people pushed past you in the halls using detailed rotoscope animations.

The Invisible Hours comes close - it's non-interactive, basically letting you play as a ghost cameraman watching the mystery.

Dark Cloudy, but it should be built around city building a bit more than combat

I mean, I don’t think it ever really became a series, but I’d love to see a modern remastering of The Suffering

CyberMage: Darklight Awakening

I'd like them to give 'Z' (Bitmap Brothers) another go.

Strange Adventures in Infinite Space

Zork

+1 for Populous.

But my answer to this every time is Red Faction (1, specifically. While I did enjoy Guerrilla, I want to see a throw back to more fully destructible environments on next gen tech).