StarCraft is balanced, gritty, and lots of fun.
Breaking free from RTS conventions of the time, StarCraft featured three playable races that differed in more than just aesthetics. The resilient Terrans, swarming Zerg, and high-tech Protoss each have their own unique styles and approaches to combat, and remain distinct from one another right down to their worker units. Yet ten years later, despite the diversity of its factions, StarCraft is probably the most balanced RTS in existence.
Story - 5/5
StarCraft takes place in a gritty, violent world with few real heroes, a couple of familiarly evil villains, and a whole host of ambiguous opportunists with no real loyalties beyond the highest bidder or the best chance of survival. Toss in a few betrayals, several layers of conspiracy, and a fourth race of mysterious extraterrestrials and you've got one hell of a story.
Graphics - 5/5
Following the usual Blizzard delays in the name of quality, including a complete overhaul of the game engine when it was mockingly referred to as "WarCraft in space," StarCraft's graphics weren't quite up to 1998 standards when it was finally released. Having said that, the game boasts some of the best graphics you're likely to find on a 2D game, and the storyline is packed with several full-length cinematics that help illustrate what your actions throughout the galaxy mean to the average guys on the ground.
Sound - 5/5
The music is memorable, the sound effects are realistic, especially for the Zerg, and the voice acting is top-notch.
Lasting Appeal - 5/5
StarCraft's near-perfect balance and strong visual clarity, which allows you to assess the way a battle is going at a glance, make it an excellent game for competitive play, while its diversity of races and range of strategic styles make it a fun and lasting game for casual play. Add in the first (and best) built-in online service made for a PC game, make it completely free, and you've got yourself a game that'll last for years.
Overall - 5/5