I love both albums with Anette. Imaginaerum is fantastic, like Evermind I would rank it second behind Century Child. I find it superbly creative and diverse.
I used to rank Dark Passion Play near the bottom, but the more I listen to it, the more I love it. The Poet and the Pendulum is probably my 3rd favorite Nightwish song, which is a hard thing to be. And there are tons of other really great songs on the album: Amaranth, Sahara, For the Heart I Once Had, Meadows of Heaven. The biggest misstep to me is Whoever Brings the Night, which is just decent, not great. Master Passion Greed is an unusual song for Nightwish, and it was tough to get into, but I like it alright by now. On the whole, Dark Passion Play ranks either third or fourth, but probably fourth, for me now—it's very close with Once.
Album Rankings:
1. Century Child
2. Imaginaerum
3. Once
4. Dark Passion Play
5. Oceanborn
6. Wishmaster
7. Angels Fall First
Still too early to say where Endless Forms Most Beautiful will fall, but I think it's most likely to come in fifth, just behind Dark Passion Play. Don't know for sure, though, because it could still definitely grow in the months to come.