If you really want to interest him in Berserk and he doesn't want to watch the 97 anime, than just show him the Netflix Castlevania. It's much more accurate to the feel and tone of Berserk than the actual Berserk movies. I'd also say that it's a better product overall. I'd compare it to how Jacob's Ladder is a much better Silent Hill movie and much more faithful to the feel of the games than the actual Silent Hill movies.
But yeah, i'm going to show him The castlevania series too. I want him to experience Berserk first.