Hmmm, I'd suggest trying Lament of Innocence since it's only like $5 now. It's not a great game by any means and it does get repetitive but it's still playable. Curse of Darkness I only managed a few levels. That said, there are good things about both games. Curse has some more open environments but it's mostly linear while Lament is somewhat open-ended (although in comparison with Symphony it's still way too linear). Also the gameplay in Lament is more polished whereas in Curse they give you a lot more weapons but the mechanics aren't as deep.
But yeah, Legacy of Darkness is way better than both of those and Mask of Shadows. I played 10 minutes of the demo for MoS and felt that it was too repetitive, I can't imagine what trudging through the whole game is like. That's one main aspect that Legacy got right over all the others. Nowhere in the classic Castlevanias did you stay in one place fighting enemies(boss fights excluded of course), they were all about continual progress and if you wanted to duke it out you could do that, but you also had the option of fleeing as well and sacrificing a hit or two to survive.
Another thing, Legacy, when you've beaten the game, you feel accomplished, like you've actually been through a real adventure. There's no hand-holding, no tips popping up on the screen, nada, it's just you and your wits versus whatever is thrown at you, just as it was with all the Castlevanias that came before. Which I guess that's somewhat of an argument against all modern games. Segmenting the whole thing down and auto saving every 5 minutes just takes away from the quintessential purpose of games.