ok it is hard to define just what is a true rts so some people may want to include Medieval Total War (or Rome or Shogun) or even other games like Sacrifice or Black and White. Well i think rts in strict terms is sc or ta.
TA imho is the No.1 rts of all time cos no other rts creates as much simultaneous screaan shaking explosiong and battle. Also TA has the most units in battle at any one time (perhaps cossacks has more but cossakcs doesnt have aircraft). TA is also the only rts with proper aircraft flight in strafing/bombing runs (sc aircraft are lame). TA AI is also the hardest of all rtses (custom content ai is truly awesome). TA strategy is very specialised and takes a lot of thinking.
I'm not sure why so many people like sc but i think its just because blizzard markets it a lto and also sc has very good strategy for an rts.
However, I wud have to point out that wb3, battle realms and tzar have increidble strategy capabilities too if people played them more. battle realms is really really good - it is the only rts with vaguely anime feel except maybe for wc3 but wc3 is kinda lame because the graphics are a bit old and its a rehash of wc2. However, I did hear wc3 had really good strategic balances and fun too.
1 rts i have not played is warhammer 40k and i heard this may be better than ta.
which ones do you guys like and why?