I have the game as well, and though it is true that all things considered Starcraft was and probably will remain one of the best Futuristic RTS's for a long time to come, Emperor is by no means bad. All I've played is single player, and as far as that campaign goes it is the longest of any RTS I've seen to date; probably over ninety missions spread across 3 different races, each one completely unique. So as for replay value, this one's a winner.
The strategy itself can, at times, get repetitive, though I find it always remains quite frantic. The graphics are gorgeous, and if you do not like the 3d perspective, you can zoom out all the way and view the map from above in 2D, à la Starcraft. In this sense, this is the first and ONLY "3D" RTS that I have actually enjoyed, since it is the only 3D RTS that is NOT painful to control and view. Other 3D games of this genre may be nice to look at, but it is impossible to get the same feel of control over the battlefiled that you get in the 2D equivalents, like in the Classic, genre defining Starcraft. One of Emperor's strongest points is that it does not suffer from this problem.
Finally, if you're the kinda guy who doesnt skip cutscenes and actually enjoys experiencing the storyline, you will be quite satisfied as the game is rife with cinematics, all professionally done in true Westwood Style (cheesy? its what we've come to expect from Westwood. Gotta love it though
)
All this being said, the true hardcore RTS enthusiast will still of course prefer such games as Age of empires and maybe even Red Alert 2. I find that if you've generally enjoyed Westwood's other titles, you will probably enjoy this one as well. And because it is so long, the money will go a long way.
Hope that helps.