I voted Top 10. If you had asked me 7-10 years ago, I would have definitely said Top 5, if not Top 3. I was WAY more into DT back then, though they are still my Number 2 Favorite Band Of All Time™. I just haven't been listening to them as much in the last 7-10 years or so. After DT12 came out, I really discovered more bands that take up more of my listening time, like Big Big Train and Haken, and others that just get more play like SB/Neal Morse stuff, anything with Andy Tillison and Jonas Reingold.
However, my favorite DT album, SDOIT, is still really high up there, and definitely still in my top 10, if I had to struggle to rank my favorites. I'm sure the likes of SFAM would be in the Top 20 as well, so among the hundreds of albums I own and listen to, there's at least a couple DT albums up there!
-Marc.