This is a hard question. I'd say it's between the Lacuna Coil EP, and In a Reverie. My favorite are: "The Secret", "This is my dream", and "No need to explain" from the EP. From In a Reverie my favorites are "My Wings", "To myself I turned", "Stately lover", "Circle", "Honeymoon suite", and "Falling". Their earlier music was a lot more experimental, I think(Voice and music). I don't know if I think they're getting worse or just evolving. I think it's just not exactly the same music as before.
Unleashed Memories actually isn't a favorite of mine, although there are beautiful songs on there, such as Halflife, Cold Heritage, Current Obsession, Stars, etc etc. And I actually like some of the songs on KarmaCode("What I see", "Fragile", "Within me" is alright to listen to every once in a while...Well those are the only songs I like. I guess that's not a good thing.) I am not sure where "Spellbound" is from, as I haven't been listening to their new stuff lately. But I like this song, especially the guitars.
I at least think they deserve their new found success, even if it's caused them to go in a different direction, musically.
I started listening to them in the 90s. The cds barely work now, lol. They skip a lot.