The Half Life franchise has a good example of a game I think would be worth completely re-making from scratch.
I know they have Half Life Source which is the old game but with some easy tweaks/updates (mainly updated textures, water, alien models replaced with their modern counterparts (I could be wrong about that)
But what if Half Life was completely re-done, so it looks very similar to HL2, but is still the HL1 story.
Even though the Medal of Honour franchise stands up quite well to the test of time (I’m currently replaying it) there are some aspects of it that would benefit from some advancements in modern games. I find that the control of the character is a bit buggy and doesn’t feel natural (jumping onto and off things is particularly bad), and the already beautiful levels would look possitively Amazing if the textures and models could be re-done (with modern shaders, higher res textures, and Higher polygon-count models)
edit: Add Wargasm to the list: Now quite an old game, had superb playability and good (at the time) graphics.
In fact, let’s make this a thread for suggesting games to be re-done with today’s technological advances in the field.