Prime example of an expantion for an already amazing game.
Warcraft 3: Reign of Chaos was already an amazing game. It brought the world of Warcraft 1 and 2 into full 3D graphics. It also added the idea of heroes (special units that are more powerful than the average units, and also leveled up as you went along). It also had an immense campaign, that added a ton of new charactors and lore into the game.
Warcraft 3: The Frozen Throne just made it better in every way. It added new units and new heroes that didn't just re-iterate what it had already done, but expand on it and fill in holes to make it an even more flexible and complex game (if it needed to be). The campaign of Warcraft 3 was doubled by this expasion. It added more levels for each race, and again added more lore and charactors, along with major twists in the plot.
The game is mechanically perfectly sound. Each of the races are perfectly ballanced; each with differenct tactics, but not one of the factions feel overballanced in any way.
On the user created content side, there are hundreds of A+ quality games out there. The most noteably famous one would have to be DotA (or Defense of the Ancients) [see the Warcraft 3 page for more information]. This is probably the #1 reason why I still play Warcraft 3: The Frozen Throne today. It is highly competative, and extremely rewarding. It doesn't take as much micromanagement (execpt for some heroes and advanced players), and is perfectly crafted and balanced. It might as well be it's own game separate from Warcraft 3. DotA has its own charactors and lore even.
All in all I could not have asked for a better Warcraft RTS game from Blizzard. Heroes are a perfect fit, the new races and units are different and fresh but still perfectly ballanced, and the entire shift to 3D has been amazing. Warcraft 3: The Frozen Throne is the prime example of what a expantion should be.
