Sorry, just postponing the inevitable here:
1. Octavarium
While many of the songs in the higher positions of the top 10 are somewhat nebulous and could jump up or down a few spots depending on my mood, this song could not. This is, in my view, the best song DT has ever released and it will be quite challenging to topple it.
It's hard to put into words exactly what this song does so well. More than any of the 20+ minute epics in the DT catalogue, this one feels the most like a cohesive piece, and that is a very wonderful thing. ACOS and SDOIT are enormously powerful pieces in their own right, so I'm not slamming them here, but 8V's movements all feel like they belong together; I can't say the same about, for instance, The Darkest of Winters and Carpe Diem, or The Test that Stumped them All and Solitary Shell.
Rather than taking any major dramatic shifts over the course of the piece, the intensity ramps up ever so slightly between, and over the course of, movements. 8V builds slowly from nothing over the course of ~20 minutes to one of the most powerful climaxes in DT history, and that's something special.
The individual lyrical threads are in themselves rather disjointed but all come together in the end, with the greater theme being, of course, "looping", or ending back where you began. Especially for late-period DT, I find the lyrics to be particularly well-done. Further, the callbacks help to tie up the album in a particularly satisfactory way; while I'm not sure I would call 8V a "concept album" in the way the phrase has come to be understood, it is certainly an album with a concept, and 8V's concept may be even more well-executed than SFAM's in this regard. A lot of thought went into this song and its relationship with the album. (I cannot, unfortunately, say the same for SC's and TCOT's "epics".)
I suppose the greater point I want to get across is this: in reviewing music, you look at the idea and the execution. With ANTR, DT had wonderful ideas, but botched the execution; I suppose you could say that TCOT wasn't exactly born out of a great idea (lyrically speaking), but it was executed rather well despite that fact. From idea to execution, I don't think DT ever did better than 8V. On the idea side, it's a thoughtfully-structured epic which grapples with interesting lyrical themes; on the execution side, the song is filled to overflowing with majestic musical themes. DT did everything right here, and that's why it's my favorite song of their catalog.
Well, that's it, then. Pols Voice, you somehow guessed my entire top 5. Congrats.