Only going to select 1 release per band or Amon Amarth would probably just fill up slots 2 to 9:
1. Dissection - Storm of the Light's Bane
Not really melodic DM, but an undeniable influence on the genre and at least similar in atmosphere.
2. Amon Amarth - With Oden on our Side
I love ALL AA tracks, except their covers. Either they cover a song that was shitty to begin with (Aerials) or they don't really improve the original (Eyes of Horror).
3. Dark Tranquillity - The Mind's I
Really hard to choose between Haven, The Mind's I and Damage Done.
Surprised to see Character & Fiction show up so much; there are a few good tracks on each, but overall they're pretty mediocre, IMO.
We Are the Void was pretty terrible.
4. In Flames - The Jester Race
Once again, hard to choose between the Jester Race, Whoracle and Colony.
5. Kalmah - Swamplord
Kalmah should've shown up on ALL lists! FOR SHAME! FOR SHAAAAAAAAAAAAAAAMMMMMMMMEEEEEEEEEEE!
6. Dismember - Massive Killing Capacity
This is what happens when a very solid DM band decides to go melodic for one release and although it's not their best, this is still a very good offering and an interesting take on melodic DM.
As a bonus this new-found interest in melody would later result in earth-shattering tracks like Where no Ghost is Holy, so what's not to like?
7.Skyfire - Timeless Departure
I just wish they'd toned down on the keyboards a bit.
8. Mors Principium Est - The Unborn
9. Arch Enemy - Stigmata
10. Amorphis - Elegy
On an unrelated note, I'm surprised to encounter such a big Nightrage fan. Only Nightrage CD I have is Descent into Chaos and I find it quite average. Not bad by any means, but profoundly average and generic.