I mean exactly what I said, and I know I listed the reasons why it sold. It STILL outsold most of the other games.
If the last two games of the LoS trilogy do well, then no doubt we'll be seeing more Castlevania titles. The only problem I really have out of anything you listed, though, was the music. The soundtrack was good, but it falls under my category of forgettable, which not a single other Castlevania title did, except for Legends.
Truth be told, with all the coattail riding, I wouldn't be surprised if there was co-op in some form in LoS2. I personally wouldn't complain about it (to each their own), but if they DID do it, I'd prefer if it were in the same vein as Halo 3 rather than RE5*.
* = Meaning there is two player co-op, but the game can flow smoothly if there isn't a second player. No forced gimmicks, etc.