I'd get rid of Command and Conquer 3 and 4 as they both messed up the series. After the failure of 3 I cannot see how they thought changing it even further from the originals was the move to make.
People would love it if they made it work exactly like the originals but with better graphics and new units (and missions/maps of course). Seriously, the simplicity of the originals (including Red Alert) was what made them so great.
As for what I would add: Psi-Ops: The Mind-gate Conspiracy. One of the only games that has a horrific story that I absolutely loved. The psychic abilities were amazing and worked brilliantly, and the physics at the time were fantastic.