I've only gotten two people a bit into DT - for my best girl friend I just made a compilation of some songs I thought she'd like, since she's not big on listening to albums in their entirety, and I've turned my boyfriend on DT by giving him Images and Awake and telling him to listen to them 20 times per day.
If a person is a potential prog-lover, they'll embrace the stuff that's harder to stomach anyway. I mean, they're going to have to get at that stuff at some point, might as well throw them into the fire right away. Even if you don't like it at once, there'll be something nagging at you in the back of your head telling you to come back to it for just one more listen, that's how it was for me. And SDoIT is one of my top five albums anyway, if I had to give people a "new" album it would be that album, not ADToE. For older albums, you can't go wrong with Images, Awake and Scenes. If the person is not too big on metal, maybe FII wouldn't be bad either.