I'm just pleased to be chatting with a fellow SC fan. :D
I've enjoyed the first SC, on all the platforms (mainly Mega Drive; but the C64 version is kinda interesting too).
I love SC2, have finished it many times. Often with different tactics. For example, did you know you can farm the Slylandro probes using the Thraddash?The Earth cruiser is pretty good for pummeling the Thrads. Do it enough and they choose to follow you due to your strength. And a Thrad can obliterate a probe using it's thruster fire - the probes just plow right intothe flame. Only in 1P mode or on easy difficulty in Super Melee mode. On the higher difficulties it will avoid this, tell me that the 1P game has the difficulty on lowest.
I finished SC3 twice. I downloaded it from Home of the Underdogs, and my dial up internet cut out so had to download it twice. But I played it eventually. It was... OK? The map was confusing. The melee somehow worse. The ships unbalanced. But I liked the claymation puppets and I liked the voice acting. The planet management was... Tolerable?
Did you play the recent sequel? I didn't like it.
As you say: SC2 was a special unique thing, and I don't think you can really reiterate on that formula. It was lightning in a bottle. The environment which they worked in was unique. They weren't getting paid, for the last 6 months it was pure crunch with no money to get it finished. They poured real human blood and soul into it. They suffered for it.
On a side note, I later go into Master of Orion due to my love of SC2. I needed more space games with interesting aliens. The first MoO ended up being a lifelong favourite game. The sequel not so much, though I know some people prefer MoO2 over the first.
It's a 4X strategy game, so a different genre to SC2. But have you tried it?