EIther The Agency or Scalebound. I don't know.

TimeSplitters 4.

A lot of the coolest scifi games seem to get canned. The original Prey 2, Battlefront 3, 1313, Darth Maul. Damn shame.

I'd put Agent at the top of my list, but that's totally getting rerevealed any time, you guys. Just watch...

I'll second both of these.  

As a fan of the Wii U, I'd have to say that BotW being pushed off for so long, then launching with features having been removed (with no attempt made to hide this fact) was the biggest disappointment I had with the system.   

The original re4. With fixed camera angles and no over the shoulder viewpoint. https://youtu.be/h_5kwX0LZAc

Oh sweet goodness... how did I never see that before? Thanks. Yeah, I think that would have been miles better if we're going on the concept of making it feel like the original games. It almost feels like RE Remake on Gamecube, but slightly upgraded. Way better imo.

Yes re4 was gonna be a lot different before the actual game we got. The first trailer I ever saw for the game. I watched it over and over in 2003-2004. https://youtu.be/DFCLu1OVmp0

Half Life 3 - Technically not cancelled, but i am ready for it, who honestly wouldnt fall back on there chair if an announcement was made at E3.(Jokes aside)

Homeworld 3 Sentinels - My all time favourite RTS series. I was so excited for this game than it totally disappeared out of existence. A Homeworld game made today at 4k with todays hardware would be incredible excluding Homeworld Deserts of Kharack being more a spin off series and different game direction and Homeworld Remastered being what it is a good Remastered / Remake. I am referring to a full fledged 3D space RTS Homeworld game like the originals based on todays hardware.

SimsVille.

A cross between SimCity and The Sims and a follow-up of sorts to the old SimTown. I was really anticipating that game. EA however had taken over Maxis at this point and I wasn’t exactly happy about this since they had already killed Bullfrog and now made Maxis shit out expansion after expansion for The Sims. Then they cancelled SimsVille altogether and that was the final drop that made me to permanently ditch the company that seems adament to destroy my childhood.

Star Wars 1313

A more recent example, 1313, cancelled by, well guess who. It looked amazing and I really liked Bounty Hunter which this seemed to spiritually succeed.

Always will be Scalebound probs. Oh and the Phantom Dust reboot.