I enjoyed a couple of days in Rome some years back.
The thing about Rome is... Everywhere you go there is something interesting to see. I was just wandering around the streets discovering intersting buildings, statues, fountains, bridges, churches etc.
What made the biggest impression on me was wandering around the ruins of ancient rome near the Colosseum. It was very stimulating to the imagination, thinking about what life was like in the Roman empire of old.
I was dissapointed with the inside of the Colosseum. You queue for ages, it is expensive and when you finally get in there is not much too see.
My advice to you is to go see some of the major attractions, like the Vatican, the Fontana di Trevi, Colosseum etc. But don't plan to much, try and just walk around and see what you find on your own, that is how Rome is best.
This is my humble opinion of course... Bon voyage!