I cant say which is the best so ill simply say which are my faves equelly
-age of empires
-Dawn of war
-Company of heroes
-homeworld
these games can usually keep me playing wheras as good as Starcraft was i actually lost interest and stopped playing eventually. Same with Middle Earth, the beauty of it and fun of having the LOTR characters to play with were strong points but imo it just didnt hook me.
The thing about command and conquer is that there is almost to tactical strategy involved. The only thing that matters is how efficiently you build your base, which can be cool, but it starts to make it more of a base building simulator than a "war" "strategy" game. In other words, what units you bring to the battle is important, but once you get to the actual battle you just sit there and watch them fire at each other. There is no point in, say, trying to out flank them, or targeting certain units first, or ajusting formations, or anything like that. It's still a great game though.
I vote command and conquer.. simply because they always bring something new and refreshing to the genre (and sometimes really hilarious stuff, like the fighting game-esque versus screens in "zero hour"😉.. and they patch the hell out of their games
only others I can think of that are in the same light are Total War series and Civ
would have voted AoE , but 3 was pretty disappointing for me
starcraft 'might' only be a one-trick pony