Warcraft 3: The Frozen Throne is the ultimate word about the multiplayer experience in RTS.
I'll list below some positive things about this upgraded version of Warcraft III:
1. Four races: Humans, Night Elfs, Undeads and Orcs. Each one has advantages and disadvantages. For instance, Orcs are very strong, but their units are more expensive and slower to be trained;
2. The Frozen Throne offers an excellent gameplay, in both the single player campaign and the multiplayer mode; this expansion comes with some new maps to enjoy in on-line matches or custom games, also with three more additional campaigns for solo play;
3. The Artificial Intelligence is unquestionably great and realistic. As you progress your skill in Warcraft III, you can raise the difficulty: Easy to Normal, and Normal to Insane. It's a good way to try new tactics, since you don't want to do this against an experienced human opponent.
4. Great cartoony graphics, amazing sound effects and a nice selection of soundtracks for each race;
5. Naturally, the coolest thing is that you can play with special units called heroes. They can become more and more powerful during a game, as you kill enemy troops and the neutral creeps around the map; The Frozen Throne expansion comes with one different hero for each race.
But there're some shortcomings as well:
1. In a custom or multiplayer game, the Insane Computer plays like a cheater: it harvests gold faster than you, so the AI may attack you as sooner as you can imagine. If you want to check this, try to save a replay of a custom game, and then watch it in the Insane Computer's perspective. You'll see its gold rising much faster than yours (+20 instead of the regular +10).
2. The upkeep is really a bad aspect in Warcraft III and slows down the flow of the game for no reason. When you reaches the Low Upkeep (when you population is above 50), your gold income rating downs to +7. And worse, when your population is above 80 you reach the High Upkeep, which means that your gold income rating downs to +4. These things constitute in a tremendous delay in the game, since the computer adversary have much more resources than you. The AI can create a more powerful army simply too early. Even if the computer didn't cheat, it would be nice to not have the upkeep disadvantage.
Nonetheless this is a good game. Again let me say that it's the multiplayer that really shines in Warcraft III. The expansion The Frozen Throne makes things even better and you'll definitely want to have this upgraded version.