This is an interesting thread. I can't say that IGA's games are totally without merit, and I enjoyed them a great deal when they were released, but he did overstay his welcome to the detriment of the franchise. I think, given what happened, he should have left after Lament of Innocence. (I'll explain later*). On the other hand, it seems like, for reasons unknown, he became the only person at Konami who gave a hoot about Castlevania. I'm not sure how this occurred.
For a few years it seemed as if Konami Computer Entertainment Kobe (KCEK) was pretty invested in Castlevania with the N64 titles and CotM. It seemed as if CotM was a response to people complaining about the N64 titles not being like SotN. In turn, Harmony of Dissonance was a response of IGA's to what he saw as the failures of CotM to live up to SotN. How that turn came about, and he was able to step in, despite CotM's success, must have been a corporate thing, with various studio mergers that were to occur (or had occurred?) Whatever the case, it seems like those invested in Castlevania from KCEK got shuffled about, and those that ended up with IGA were basically beholden to his vision of the franchise.
In 1999, Director Yuji Shibata and Game Designer Takeo Yakushiji (who worked on both N64 titles) had this to say about Castlevania in a Legacy of Darkness interview at IGN.com (excerpted below):
IGN64: As a designer, what strategic and/or product decisions do you take into consideration when continuing the Castlevania line?
TY: The Castlevania series has always had a theme of horror behind it. This does not mean bloody scenes or chilling torture, but a mood of darkness and absence of light, that still has cool beauty and elegance to it. Retaining this theme has been what I have been careful with while designing the game. In regards to the character design, I have tried to bring the former enemies to life in 3D and retaining their atmosphere, while keeping them appropriate and looking cool for this generation of game system.
IGN64: How does the technology of the N64 impact your design decisions?
YS: The limitation on the number of polygons that could be on screen and in the enemies. Also, with the lack of memory space, the number of enemies that could be running around on screen at one time.
TY: The anti-aliasing technology worked very well in this project. Even with a limitation of color, we were able to create stunning visuals, even in Hi-res mode. Also, with putting different shading on the texture giving the illusion of depth and distance, it was easier to create compelling levels.
IGN64: What was your most satisfying product to work on and why?
YS, TY: (In unison) : Castlevania Legacy of Darkness of course. (laughs)
TY: In the previous version, we learned how to use 3D. With the knowledge that we learned, we could take this version and refine the look as well as increasing what we did with the visual look and the feel of the game. With this, what we have especially made an emphasis on is creating stages that had a lot of action elements in fully detailed rich 3D environment.
IGN64: What did you learn from your experience of making Castlevania 64?
YS: How to program in 3D and make a 3D action game.
TY: When production first started, I looked upon it as a challenge to go from creating a 2D game to a 3D game. My past experience was all 2D, so working with a 3D world environment was a challenge, but was exciting. It was like being asked to make my own amusement park.
IGN64: What's the weirdest thing that happened during the making of Castlevania Legacy of Darkness?
TY: This is something that happened while we were making the former game. We wanted to get information on Dracula, so we went to an event that was celebrating the 100th anniversary of Bram Stoker's Dracula. What ended up happening was that we were put into a small theatre with no bathroom, and got stuck watching eight hours of minor Dracula movies that were not even sub-titled. Suffice to say, we didn't learn a whole lot from that process.
Say what you want about the N64 titles, but it seems like these guys were all in, learning on the fly and eager to maintain a strong Castlevania brand that was true to its roots, whatever that took. So what happened that they and/or KCEK were replaced by IGA? Was it all just a corporate thing?
*Regarding IGA's history, here's what I have to say:
-Whatever his true roles in Rondo and SotN, they were solid entries that mixed things up. Not my favorites, but not negative if taken by themselves by any means. The problem was that they set trends that were later set in stone as a new definition for Castlevania.
-Harmony of Dissonance was interesting, but felt somewhat less polished than CotM, which I bought with the GBA and enjoyed more.
-Aria of Sorrow is a solid entry that is most remarkable in its shock value (story/setting) and more polished visuals after HoD.
-Lament of Innocence was a game with good intentions and great atmosphere, but it ultimately fell very short, especially in retrospect. (Still, it's ironic that Lords of Shadow, while slightly more ambitious, contained many of the same pitfalls as LoI. If you play the two next to one another, graphics aside, you see that not a lot has been learned in the years between them. KCEK was really ahead of the curve, but all their design work was dropped).
Here's the problem, all of these IGA games were fine at the time, and they still have their perks (particularly with regard to music, some of the atmosphere, and some of the art choices), but none of them had the same staying power in game design as earlier entries for me. I lose interest in them quickly when I play them these days. Perhaps SotN and CotM (which isn't IGA's), came out the best in the long-term. Hard to say...
But my MAIN point is, IGA hit his apex for moving the series forward at LoI. I thought he might turn a corner there and really capitalize on everything. Instead, Curse of Darkness decided to expand on LoI's flaws and add new gimmicks to pad the experience. Dawn of Sorrow was essentially an updated AoS with better graphics and a worse story. Portrait of Ruin was a much more interesting attempt to meld Castleroid and Classicvania, but the Classicvania parts did not understand the game design of Classicvania, resulting in just mini-Castleroid design in a larger Castleroid castle. I never did get to play Order of Ecclesia. I was burned out on Castleroid-anything. But it didn't seem to out-and-out solve PoR's shortcomings, despite some baby steps in the right direction here and there.
Instead of getting Classicvania overload, we got Castleroid overload. Either could be detrimental to the series, but history had it on the Castleroid side. That IGA could not see where the fundamental improvements needed to be made after so many games, and just tried to cover them up with side-steps and gimmicks, sadly showed that he should no longer head the series (and no longer does). I appreciate his efforts, but he overstayed his welcome. Honestly, nothing really got fundamentally better in execution in game design post-AoS for his 2D games, and LoI for his 3D games. (Actually, you know, Judgment, its monster stages, while not great, were maybe a small step in the right direction at a tech demo level; but that was a side point to what was basically an amusing fan-service fighter. The wrong game at the wrong time).
However, I don't like what's happened with Lords of Shadow's Mercury Steam and co, either. I think they have the wrong idea in a whole different way than IGA. The only things they got fundamentally right, IMO, was a few set pieces, stage-by-stage structure, the need for a whip hero, and for said whip to be able to be used in a variety of ways in the gameplay. In terms of story, overall art direction, and especially gameplay/level design, it almost shoots just as wide as Curse of Darkness, though is maybe more inherently fun than CoD...
In short, I really wanted the KCEK team, especially the members of the N64 games, to get a shot at Castevania in 3D again. (They were setting the building blocks for a more diverse CV future). But now they won't. And I don't know if anyone has the vision to do Castlevania right in 3D, which would mean going against conventions set by "popular" modern franchises like God of War.
Regardless, outside of Castlevania Rebirth, which works more as a stopgap than a full solution, I agree with the sentiment that Castlevania has slowly lost its identity--it's "special something"--and Lords of Shadow was the culmination of that feeling for me. What IGA was doing was making me shake my head--it often felt like a increasingly silly, "fan-service-y" stage of development that it would eventually grow out of. What Mercury Steam has done has all but made me close my eyes and scream.
EDIT: At the risk of rambling, here's the thing. Mercury Steam may get it in its head that all it needs to do is make the game "look/sound" more like Castlevania in terms of villain set/music, etc. (And it'll probably get brownie points for that). But then, think about it, we'll just have a glorified LoI. The gameplay needs to be fundamentally changed to allow for true and distinctive "action-platforming," as I've noted in other threads. The design paradigm set for LoS does not allow for the maximum usage of the Castlevania property.