Starcraft is easily the most engaging and well-balanced strategy game ever made.
There are many reasons why the game is suited to the startup guy. Average games last 30min, which is perfect for someone who has a life and other things to think about. The game is easy to pick up, but always remains challenging. The ranking algorithm does an awesome job of matching you with people your level, meaning that you don't need to invest too much into the game for it to become fun.
The biggest failure of most games is that unless you're a "hardcore gamer," online play with better but anonymous players can be an infuriating experience. You'll get your ass kicked, while everybody flames on you for being a "fucking noob." Starcraft overcomes that by using an insanely great matching algorithm, and having a game that is well balanced and appeals to any level.
I don't spend much time playing games, but the few times that I do it is always Starcraft II (or Warcraft III), and I always have a great time while stimulating my intellect and reflexes.
