Did not buy this until 2005 and although it is a better than average game, I think looking back that it was over-hyped.
At the time of it's release it was an RTS with several original features such as hero units and special abilities. It is somewhat like a role playing game but it's pretty light in that aspect but there is some basic character enhancment. Warcraft 3 has quite a variety of units and tactics you can use in battles among the four races and it is very well balanced. Every race has units that are equivelent to other units in another race without being too similar. You can really notice the different style of each race as well. For instance, humans have more traditional knight in shining armor units and are fast builders. Undead have large numbers and regenerative spells that goes hand-in-hand with their tendency to be hard to kill (since they are already dead). Orc's are akin to the protoss of starcraft in that each unit is very powerful and resiliant. Brute force is their style. Nigh elves have mobile bases and make heavy use of magical spells and are more one with nature than the other races.
Although the graphics were designed to run the game well on a wide range of systems, they still are quite impressive. Warcraft features vivid, colorful environments that look somewhat cartoony but lush at the same time. Units have a lot of detail and are well animated but unfortunately suffer from an extremely low polygon count making them look very blocky when viewd close-up. Special effects like spells, explosions and aura's look fantastic.
On the audio front the musical score is well composed and makes you feel part of the Warcraft world. Sound effects are loud, clear and crisp and the voice acting is well done.
The gameplay is pretty similar to a lot of other RTS games but a bit different because the focus is on smaller armies where you will be using their special abilities more often than just sending in waves of weak units. It makes the battles intense and more strategically satisfying. The game tries to mix it up by including dungen crawls with fixed number of units and side-quests but it doesn't make that much of a difference.
One thing I was dissapointed with is that this game doesn't seem to stand out from the crowd much anymore. It could be that I'm playing it 3 years after it's release but I thought the game would immerse me a lot more than it did. I did like the story but the CGI cutscenes between campaigns were a big let-down because they were so short and simple. I honestly don't know why this game was so long in development. It is definitely a fun RTS game to play that has a unique flavor but I can easily say I enjoyed Rome Total War and Starcraft much more.
I don't know if Blizzard will ever be able to top the venerable Starcraft franchise unless they make a sequel which I hope they will sometime this century.