You're arguing your case by comparing a character who had ZERO screentime with people who had "barely 10 min of screentime". Vergil was a non-existent background character in DMC1 just like Eva was.
Your argument holds no weight.
They are not assumptions! The f#cking games told us that sh!t. Here's a timeline for you...
Eva and Vergil killed when Dante is young (told to us in DMC1)
Dante meets Vergil for some shenanigans a year before DMC3 (DMC3 told us this)
Dante and Vergil fight in Temen-Ni-Gru (f#cking DMC3)
Dante fights Nelo Angelo on Mallet Island and learns that he is Vergil (f#cking DMC1)
That is literally what we were told! The goddamn games themselves are the definitive proof.
So a gain you ignore that Eva and Vergil were counted together as a subject, and since Eva was killed, the implication is that Vergil was to.
Yes, there are plenty of ways "lost to evil" can be taken, but because we knew of Eva's fate (which she shared with Vergil), it means killed by demons. Just because we know Vergil was alive for DMC3 means nothing, because you can't bring knowledge of DMC3 into this argument.
I'm criticizing DMC1, and how it was when it came out.
What the f#ck are you even talking about? That's the whole goddamn point of this! The game forces you to think he's dead because everyone in the game says so! That's what the twist was supposed to f#cking BE, that "Surprise! Vergil wasn't dead but was Nelo Angelo this whole time! And you just killed him! Gratz!"
I'm not even arguing that. This whole time I've been arguing that Vergil wasn't developed at all for the twist to be dramatic. Pay attention...
No, because in DMC1 Trish says "You're the man who lost a mother and a brother to evil twenty years ago". Eva and Vergil were lost in the same incident. In DMC3, Vergil wasn't defeated by Mundus until...what? A year or so before DMC1? Those don't sync up.
Except for the aforementioned desync in events above
It's just as tedious as you trying to force a reinterpretation into the discussion where it doesn't fit. Stop throwing DMC3 into this.
Uh...no. It was always a huge talking point within the DMC communities that the franchise's canon was jiggered because of all the different writers' hands the series passed through. This was before DmC was ever even a thing. Hell, if people weren't talking about gameplay mechanics or new tricks, it was invariably discussion on "wait, was this novel canon? It explains this" and all that.
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Here, let's get the criticism of mine straight, for future generations, shall we?
DMC1 did a p!ss-poor job of making the audience empathize with the tragic twist of Nelo Angelo being Vergil. We were explicitly told throughout the game that Vergil supposedly died along with Eva twenty years ago, but ta-da~ he's been alive this whole time as Nelo Angelo, whom Dante invariably kills and feels remorse. It's extremely difficult for an audience to empathize with Vergil/Nelo Angelo, and by proxy even Dante himself, because Vergil had no character development, or more succinctly no character at all with which to empathize with. He wasn't some hero tragically turned to the dark side, he wasn't some character pushed to his limits until he broke, he wasn't anything. He was simply a name.
DMC3, however, made the Nelo Angelo twist a bit more dramatic because Vergil is an actual character, but in doing so also still ruined some of the overarching narrative, because the events and information from DMC3 didn't jive with what was told in DMC1 where Vergil was killed at a young age along with Eva, something corroborated by Dante throughout DMC1, and perpetuated by all of the characters - even the ones who know that Vergil is still alive.
Put simply, in Dante's eyes, he knew both Vergil and Eva had been killed, and believed so until Nelo Angelo's identity was revealed. Then, in DMC3, we see that Dante has known Vergil was alive for several years before DMC1 with all of their past run-ins, which directly contradicts Dante's own belief of Vergil's death in the first game.
The lack of foresight in the franchise has left us with a hodgepodge of canon with a lot of questionable content. Especially since Kamiya hates making sequels, so he never made DMC1 with any broader narrative in mind.