Happened with me when I picked up Castlevania: Portrait of Ruin. The last 2D CV game for me was SOTN, and I enjoyed that too, despite never having finished it since I got stuck. I did play Lament of Innocence, and it was fun, but using 2D mechanics in a 3D game (ie, the jumping mechanics) made it too frustrating for me to commit to. So here I am playing POR and I’m enjoying it as much now as I did playing SOTN. Of course now I’m stuck…again, but oh well.
I used my old copy of Saga Frontier, which I haven’t played since oh, 2000 or so, to test my PS2 after it was fixed, just because it happened to be the closest game at hand… and now I can’t stop playing it all over again. 
Seriously this a good (if flawed) game, that could’ve been just GREAT if only they’d finished it properly before release. Square should remake it for the PSP or something, I’ll bet it would be a hit
DR, try to get your hands on Dawn of Sorrow and Order of Ecclesia, which are both better than PoR imo. When you finish PoR make sure you replay the game in Sisters mode. It’s controlled solely by D-pad and stylus and it’s really fun.