I was a player in an evil campaign some time ago. Evil campaigns can be awesome if played right. Find a reason for a party to bond and give them a goal, and you can have an evil campaign you'll never forget. Here's an example from my own experience:
Being evil characters, we approached problems differently than a good or neutral aligned party. We used necromancy and raised undead servants. We tortured those we captured whenever it was necessary to get information. We held little regard for the lives of those that crossed us and took no prisoners unless we needed them for something.
However, we were kind to all the normal people we met. The townsfolk. The fishermen. Farmers. And there was a really good reason for that: We planned to rule the world. Might as well have everyone love us once we did.
The plot of the game involved an evil tyrant who controlled the land. His armies were massive, often cruel to the regular folks. He took their money and left them starving. He killed those who said things against him or who dared to defy his orders. Under his control, the land was in misery.
We used our evil to our advantage as we slowly and methodically began dismantling his army. We spread disease to his men, poisoned their food, attacked them with undead minions of their own fallen comrades, killed them in their sleep and left our calling card. We wanted the tyrant to know we were coming for him. We were brutal. We used guerrilla warfare and hit his army when they weren't looking, turned them against each other with lies and treachery, and infiltrated the highest ranks of his men.
As the final insult, we earned the right to work for him. So, we pretended to do his work. Those he wanted killed, we turned them into allies. If he wanted us to take an armed force to wipe out a village, we murdered the armed force and replaced them with people from the village. Our blood was all over, and he didn't see it coming.
Once we had weakened him enough, we stormed his castle and killed him in front of an assemblage of his followers and right in front of his family. We took his throne. We were evil, but we had made the world a better place, and the people followed us. Because sometimes, to beat evil, you have to be evil.
So, yeah, evil can definitely be done right. The trick is to give the players an evil even bigger and a motivation to end it. As my character used to say: "Can't let someone else rule the world. That's my job."