I've finally gotten around to playing Castlevania: Symphony of the Night... and honestly I don't see the big deal over it. It's likely due to me playing other Metroidvania games before that one, which was what started it. Portrait of Ruin was my first Metroidvania game and I liked it... then it was Order of Ecclesia and I liked that one better because of the way the stages and the map screen were set up. I played just a touch of Dawn of Sorrow but really not much, and then finally Symphony of the Night this past weekend.
To be fair I don't get the appeal of the Metroidvania style. I was never a fan of Metroid so maybe that's it, but I prefer stages. Sure, they don't have to be super linear stages like the older games, but they can be somewhat expansive like Order of Ecclesia had it. There's too much backtracking and overall similarity when you have an entire castle to explore.