Rise of Nations is one of the best games that I have played in the multiple era RTS games genre.
1. Gameplay - Well! There isn't much to say as far as gameplay is concerned. 'Superb!!' will just hardly describe it. Following the lines of the Empire Earth series, Rise of Nations will allow you to span from the Dark Ages to Modern Age. But unlike Empire Earth, this game has a much better feel. While Empire Earth started off from the Prehistoric Age and ended landing you in some weird future, Rise of Nations is more passable. It starts from Dark Ages and unlike Empire Earth, people don't fight with bare hands. It also ends in the modern age with the most advanced units you are capable to build are the Stealth Bombers and Advanced Jet Fighters, unlike some flying robot-thing in Empire Earth. The interface is quite pleasing and the basic gameplay is quite likable.
2. Graphics - Rise of Nations implements quite advanced graphics rendering techniques and allows you to zoom in to a certain degree to get a better view of the battle field. However even with such capabilities it cannot match the finesse that was present in Age of Empires II. Even with the minimalistic graphics, it created a superb effect. So to say and considering that Rise of Nations is an RTS game, I would say that the graphics is quite commendable.
3. Music - Well an RTS doesn't need music, but Rise Of Nations provides you with one. I never payed much attention to it, as there are more pressing things to do in the game rather than listening to music. However the music at the menu is not bad. A not impressive performance on the music on a whole would be my verdict. But please let this not deter you from buying this game.
4. Conquer the World Campaign - This is one of the most immersive parts of the game. Here you get to play as any one nation and you battle other nations for a complete domination over the world. You have a separate interface for the campaign, where you will be provided with a world map with various countries etched out on it. And with your and enemy armies placed on various countries. All you have to do is to drag your army and drop it over some territory/country that you wish to conquer. After that a normal Rise of Nations war starts off. Capture Supply Centers to create a new army. Also attacking a non-capital country with a reinforcement strength such that the total number of attacking armies are 2 greater than the total number of defending armies, then the territory automatically passes on to the hands of the attackers. This however occurs with territories with territory strength less than 4.
On a whole I would say that Rise of Nations is simply put a must-have game.