The amulet was always a supernatural item, even back then Perfect amulet + Force Edge makes the Sparda sword, though there is a scene later on where it's seen separately, probably for the sake of drama. DMC3 only made it also be a key to the demon world.I know it isn't Kamiya's game, but anyone with common sense would take in to account the game's predecessors when working on a prequel. And don't take what I said about DMC 1 literally.
If Kamiya was still on board this franchise throughout, DMC 3 would have never happened the way it did.
It's kind of a thin excuse saying it was Dante only remembering what he wanted to remember. Sure it was a happier memory, but he doesn't have many memories with Vergil.
We're told he lost his family 20 years ago. He's 28 in DMC 1. When he defeats Nelo Angelo, he only finds out it was Vergil when he discovers the amulet. The amulet also I'm guessing in Kaimiya's mind at the time, wasn't a supernatural item, but simply a family heirloom.
Seriously, even Kamiya talked about this and doesn't agree with the liberties taken when it came to DMC 3. That kind of story was never supposed to happen. Vergil was supposed to be dead and gone. Not somehow being a d!ck about things and seeing his brother off and on in the past decade.
Nero is definitely the walking plot hole.
Yes, Trish said he lost mother and brother 20 years ago. Dante could have easily thought she doesn't know about events of Temen-ni-gru. He could have also thought Nelo Angelo was just another devil playing tricks on him. It's kinda hard to expect brother you saw fall into demon world 9 years ago to show up on that very island and on the side of the bad guys, with a different fighting style.
Thin excuses... maybe. But DMC3 is canon, so you'll just have to learn to accept that fact.