Stigmata for me. All three albums though are criminally overlooked.
Are they though? Arch Enemy is generally one of the first half-dozen or so bands brought up when melodeath comes up, and the first three often seem regarded as the best. I guess it depends on what crowds you're around. I agree that they're great, but there are dozens and dozens of other bands who don't much attention at all.
I agree they are one of the most successful melodeath band....but didn't they become so after Liiva left and Angela Gossow came on board? It seems to me they became much more of a "phenomenon" (relatively speaking, of course) at that point, while before they were very much a niche band (with "famous" members, sure, but still within the metal scene). My guess is if you ask fans now, they probably don't know much about the first three albums, but I might be wrong...
Maybe my perspective is skewed, but discovering the style in the early 00s, the big names were In Flames, Dark Tranquillity, At The Gates, Soilwork, Carcass, and Arch Enemy. Maybe throw a couple bands like Amon Amarth and Children of Bodom in there as slightly more distant ones. Those are still the most common names you see on recommendation lists, with a few newer bands sprinkled in sometimes. I was probably reading discussions from too many elitists, but it seemed that everyone was blasting
Anthems of Rebellion and beyond and talking about how much better they were in the 90s, and if you look at most aggregation sites, those all tend to have lower ratings than the first four albums. Perhaps we are at the point where we're distant enough from them now that newer fans neglect them, but at least they're still a pretty big name and that will get some people looking into the early albums. But then there are so many other great bands that didn't even get much attention when they were more current, Satariel, Ebony Tears, Callenish Circle, Nonexist, Torchbearer, etc.