Maybe? Depends on what you mean.
From a business perspective, he helped to give Castlevania a consistent public identity, and he put out titles on a regular basis. He put in a long tenure of keeping the series running, and made a lot of solid games (though few spectacular ones). Unfortunately, the decisions he'd make (or sign off on) in the long run would cripple the franchise, IMO.
If indeed he was involved to the extent that some argue, Symphony of the Night is likely his crowning achievement, Aria of Sorrow was a pretty creative follow-up in plot and gameplay, and The Adventure Rebirth was a nice try to turn things around in the spiritual sense.
But this insistence of keeping Metroidvania-style forever, with significant changes coming too late and coming in often unpolished or strange forms, really limited and hurt Castlevania. Also, the decision to completely abandon the legacy of the N64 games in favor of following contemporary trends like Devil May Cry for Lament of Innocence, and watering it down further with Curse of Darkness, destroyed any chance at public credibility Castlevania had in 3D. Cox's Lords of Shadow, for all its tweaks and graphical polish, is still following the tradition IGA set down for 3D Castlevania with Lament of Innocence. I'm not saying LoI and CoD were without their positives and/or charms, but their fundamental flaws set the public/fan opinion on CV in 3D in Medusa-made stone, and made designers look further and further outside of CV's history for inspiration.
So, you could make a case for both sides...but I'd probably only have one game he worked on in my top ten games. Personally, I would have hoped that Castlevania was passed around to others during that time; but perhaps no one else wanted to take a crack at it in the company. The interviews with the N64 team seems to suggest that they had a more rounded view of the franchise.