Interesting that whilst the original thread question seemed to refer to Starcraft and Warcraft II, quite a few have decided to mention Warcraft III instead. Hmm. I often wonder how many gamers are keen to talk only about the latest' stuff blindly ignoring the past and what's gone before. Oh well. I'll do my best not to gripe too much.
I thoroughly reccomend Warcraft II Battle Net Edition, which contains both the brilliant original game and the expansion, beyond the dark portal.
I enjoyed Warcraft II alot more than the derivative (warlords battlecry anyone?) Disney-esque (where's the gore and eerieness from the original?) Warcraft III, which I was quite disappointed with. Being forced to play humans from the start as opposed to the original two where you actually had a choice between orcies and humans got it off to a very unfortunate start.
Lucky the cinematics were good - however, they don't make the game now, do they?
My friends and I have been having quite a few Warcraft II BNE sessions of late and its been great fun. It represents for me the sweetspot in RTS games with C&C and Red Alert. And the music is perfectly suitable and so memorable!
Thus, I really reccomend it!