I was extremely disappointed that Ressurrection got the axe. I bought the Dreamcast on day one and that was one of the games I was looking forward to the most. Now that I look back at it though, it may have been for the better. All I see in screenshots are bare, square rooms. I have the inkling now that it may not have been particularly good. Regardless.. I'd be lying though if I said I wasn't curious to see how it would have turned out.
(the rest is somewhat trailing off-topic, more-so relating to the other games people here have mentioned)
I thoroughly enjoyed the Nintendo 64 games. Legacy of Darkness is the larger game of the two, but strangely I prefer some of the level designs (and higher difficulty) in the original game than I do LoD.. Regardless, both are worth owning IMO if the proper time and attention is given to them. RetroSnow did a great review on the first one and really puts it in it's deserving place.
In regards to the talk about the PS2 games, those are mixed for me.. I really liked Lament of Innocence when it came out. Awesome visuals, awesome music, awesome gameplay mixing both styles the series is known for, awesome boss fights. Good secrets. Not so awesome story or voice-acting though and that's what keeps it from being excellent. Regardless, it's worth checking out IMO and I wouldn't have minded the series to continue in the direction this one was leaning towards.
Curse of Darkness I found to be mediocre at best. I was stoked when I heard it was heading back into more of a SotN direction, but was severely disappointed as I trudged through this game. Weak boss fights, extremely repetitive and monotonous level designs (one long corridor after another, typically), weak enemy designs that also get the palette-swap treatment as the game goes on, and another terrible story with equally poor voice-acting. Ugh. Like someone else mentioned, the leveling-up and upgrade system was cool, but that and the soundtrack is really all it has going for it. I think it would have been better for Konami to release it as a different game altogether, not a Castlevania.