Not the same thing. The 8-ball is no different than dice. You randomize the result by shaking it. With a Ouija board, you invite spirits into your body to control your actions. There’s nothing random to it.
What kind of spirits? Supposedly of dead people. But dead people are in Heaven, in which case they’re saints and would never participate in something like a seance, or in Hell, in which case they are subject to demons. (OK, we Catholics believe in purgatory, but people are insensate while in purgatory, like Lazarus and the rich man, neither of whom could communicate with the world.) So really, you think you’re asking your great Aunt Mildred, but it can’t be Aunt Mildred, so it must be a demon pretending to be Aunt Mildred.
Now, you can say that you don’t believe that demons can be summoned through a mere cardboard game. But it’s not the cardboard that has any power; it’s the person seeking communication with the spirit world that does. You also may not believe that such a person has any power to summon demons, but then if you believe that, why would you pay twenty bucks?
The real danger is that the power of a Ouija board lies in the shadowy zone between the merely psychological and the spiritual. People “play,” not realizing how much power psychological effects can have to reveal stuff to us. (For instance, a girl asking the Ouija board who she’ll marry reveals her own desires, hopes, or expectations.) Once the psychological effects are revealed (and they can be quite powerful for some people), the temptation comes forth to go beyond harmless play and into really dangerous spiritual territory.