I believe that the second Starcraft does the first more the enough justice.
The game play is quick and intuitive but easy for new players to learn and veterans from SC1 to pick up.

As for balance, it is an ongoing process, with the patches to change unit damage and everything (Banelings are massively overpowered lol).

In General SC2 is good but there is still a bit of fine tuning to do but after they are finished the fixed balance should make the game one of the best RTS games ever.