Wow, if that isn't a list of personal favorites I don't know what it is. There are quite a few better ones out there to include some more recent ones. Most of them have been already mentioned.
My favorites are: C&C Generals Zero Hour, Red Alert 2, Total Annihilation, Grey Goo, and Ashes of the Singularity, plus a few more on this list (SC2, Company of Heroes, and WiC). Ashes is debatable because it only has two factions though it is a very beautiful game. The devs remark the game is not designed to cheat but they mention they have programmed the AI with faster production at the higher difficulty levels, which is still cheating. I would honestly prefer the AI be able to see the map and all my units than to have that, but that is just me. Ashes is an extremely beautiful DX12 game and has some great features but still lacks in many areas that have been a part of RTS games for years now.
My favorites are: C&C Generals Zero Hour, Red Alert 2, Total Annihilation, Grey Goo, and Ashes of the Singularity, plus a few more on this list (SC2, Company of Heroes, and WiC). Ashes is debatable because it only has two factions though it is a very beautiful game. The devs remark the game is not designed to cheat but they mention they have programmed the AI with faster production at the higher difficulty levels, which is still cheating. I would honestly prefer the AI be able to see the map and all my units than to have that, but that is just me. Ashes is an extremely beautiful DX12 game and has some great features but still lacks in many areas that have been a part of RTS games for years now.