A timeless classic that will be around for a long time to come.
The game-play is rather simple and i for one loved the fact that you can only build units to a limit of 100 food units, that's around 10-20(add or take) troops depending on their level. It's a game about skills, it's not about how many units you have, it's about how you control them.
For me, WoW came about 1 year after i played War 3 and i have to say that this way (War3 first than WoW) is much better than the other way around. It's better to see the "limited view" of an area and know its history first and explore it in detail and have a lot of fun running around it (like in WoW) later.
Each of the 4 races available in War 3 ( Human, Orc, Night elf and Undead) has its own unique charm, its own story and representative characters and units. I for one can't decide which i like better (I'll have to go with undead for the moment) and i always change my favorite race in a month or so; it's more fun that way.
The last thing i will discuss here is the alternation between the races as you follow the campaigns. This is a characteristic to blizzard games, which is to play every race at a time, often having to beat those you've enjoyed hours before.
All these said, War 3 is a great experience and a "must have" for RTS fans everywhere as well as for RPG fans.