Red Alert 2 & Yuri’s Revenge are my favorite games of all time. I sunk so much time as a kid beating the campaign and then making custom maps and levels for fun. The installer and the cut scenes were so memorable. It also had an amazing sound track. It was also one of the few RTS I tried at the time where the game didn’t feel like it took forever. For contrast I remember playing some C&C and also Dune 2000 as a kid and I remember each campaign easily taking over an hour to complete. I also remember it got kind of boring fast.
Aside from those some other honorable mentions:
SimCity 3000: My first sim city game. It was fantastic with an amazing sound track.