I put Amaranthe's self-titled debut on roughly the same level as Cyhra's first album. Some good songs, some so-so songs. It's okay.
The Nexus is legit one of my favourite albums though. I enjoy every song on it from beginning to end. I really dig the dystopian/mecha vibe going on throughout the album and think they did a great job telling that story.
My favourite song off it is probably Mechanical Illusion. It reminds me of a Scar Symmetry song with some extra female vocals. The production is nice and clear, riffs are really solid, the vocals all sound great, the lyrics are decent, the solo fits in perfectly and the electronics add to the song rather than take away from it.
The title track is my second favourite, for similar reasons to the above, although Elize is a lot more prevelant this time. The chorus is just ridiculously catchy to me. Very pop and very cheesy, but hey, as a big power metal fan why wouldn't I love that?
Can't really speak for anything after this album as I don't have much interest in Amaranthe after this point. First two albums definitely hit all the right spots for me personally though.