1. The ending of Dracula Densetsu II/Belmont's Revenge
In the ending it says Dracula was defeated because of Christopher's love for his son and that Soleiyu would succeed Christopher as vampire hunter. In then says the following: "このごベルモンド血すじはバンパイアハンター・ディーとしていくた伝説を生み語りつがれていくことになる。"(From then on it had come to pass that many legends about the Belmont lineage as vampire hunters would be passed on). I'm sure how clear this is reflected in my translation, but this definitely states that from this point forward the Belmont family would become vampire hunters.
Not "become vampire hunters", but be well known as vampire hunters. What is implied here is that they become famous.
2. The manual/opening narration of Akumajou Densetsu
ここにきて正教会はついに、太古にまでさかのぼる古い血筋を持ち、忌まわしき者達との戦いの中で生き延びてきた一族である真正ヴァンパイア・ハンターと呼ばれるベルモンド家にワラキア討伐を依頼することとなった。(Eventually the Orthodox Church decided to request the Belmont family, a family possessing an old lineage dating to ancient times who had survived battles with abominale beings, and were called genuine vampire hunters, to go on on a elimination mission to Wallachia.)
The problem here is that you're assuming that they are being called genuine vampire hunters by the general public. It is not specific and it could mean that they are known as genuine within the church itself.
I think it's logical to conclude that 2 follows from 1, correct? In Christopher's time the Belmont family are established as vampire hunters, and by the time of Akumajou Densetsu they had built up their reputation as "genuine vampire hunters" (and before that they had been exiled). Although IGA placed it first in the timeline, nothing in Akumajou Densetsu outright denies Dracula and the Belmont family had a conflict before. (I made to sure to check that).
I could just as easily say the opposite if I assume that the Belmonts were only known as genuine vampire hunters within the church and that the general public didn't know about them outside of being being feared by whomever it was that exiled them.
Another small part of this puzzle, yet an important one, is the following. This is from a fan interview with the scenario writer for Akumajou Densetsu:
Q: 889: ラルフ・C・ベルモンドのCはクリストファーだったのでは? ドラキュラ伝説が同時期に出て年表がおかしくなったのは社内打合せ不足?
A: 890-891: > ラルフ・C・ベルモンドのCはクリストファー です。表の資料に書いてあるかどうかは知らないけど。 > ドラキュラ伝説が同時期に出て~ 違うチームが作ってたからじゃないかな。その時はもう自分居なかったし。○松さんはその辺こだわる人じゃないように見えたから、そのせいかもしれない。IGA体制後に関しては全く知らない。[...]
Q: Did the "C" from Ralph C. Belmont stand for Christopher back then? Did the condradictions with Dracula Densetsu, which came out at the same time, occur because of lack of internal meetings?
A: The "C" from Ralph C Belmont stands for Christopher. I don't know if this is written in the instruction manual. I wonder if it was because Dracula Densetsu came out and was developed at the same time? At that time I wasn't there anymore. Matsu-san didn't seem like the person who occupied himself with those things, it might be because of that. I'm not at all familar with the IGA system that came afterwards. [...]
This seems to clearly indicate that there was not a lot of focus on details and continuity.
So I think that given the above statement and the fact that Akumajou Densetsu takes place 100 years before Simon's era, it can be concluded that Ralph was meant to be the same person as the Christopher who was mentioned to have defeated Dracula 100 years before in the Famicom Akumajou Dracula manual. Christopher in the Famicom manual was said to have had a confrontation with a revived Dracula, so that would be evidence for Dracula to have revived pre-Akumajou Densetsu.
Doesn't it say that AjDen takes place "more than 100 years" before Simon as stated in the manual?
I agree it is likely Ralph was intended to be Chris originally, but that is not the case in the end.
The manual of AjDrac does indeed say a Chris fought a revived Dracula, but that is not evidence for it being AjDen instead of DDen.
Anyway, it appears that by Simon's time, Ralph became known by his middle name Christopher in the legend that was passed down afterwards. This seems to create a bit of an odd situation where there exist two Christophers: The Dracula Densetsu Christopher and Ralph a.k.a Christopher.
This is a pretty big assumption that complicates the situation more than it solves anything. And it hinges on other assumptions being true as well. I don't agree with this at all.
In think this might also explain why Dracula's age is given as 800 years in the Rondo of Blood manual (before the Mathias Cronqvist story was even conceived). Akumajou Densetsu kind of seemed to imply Dracula was the historical Vlad Tepes. However, since the Dracula Densetsu games supposedly take place before that, it opens up the possibility of Dracula being older. Also, there's a magazine preview for Rondo of Blood from a Japanese magazine that seems to imply the order Christopher --> Ralph --> Simon.
I would argue that every game in the series implies that CV Drac is analagous to RL Drac simply because of the name.
Dracula the vampire in the his first literary appearance is outright stated to be one and the same being as Vlad III.
At this point we still only have one solid century to work off of; the 15th as stated in the manual and intro of AjDen.
But then SotN happened...
Dracula's True Origin - [1792-800 = 992]
AjDen - [1400s = X-(100+U)], more than 100 years prior to AjDrac. Best guess is that according to AjDX2 this game must take place in ~1470.
DDen - [X-100 = 1592-V*100], 100 years prior to AjDrac. At minimum this game must take place in 1492.
AjDrac - [X = 1692-V*100], at minimum this game must take place in 1592 according to AjDX2.
Prior to AjDX - [W = 1692]
AjDX - [X+Y*100 = W+100=1792], 100 years after the prior battle. SNES version states multiple centuries since Simon. PCCD manual states Dracula is "800 (?)" years old.
AjDX2 - [1792+4], the Richter vs. Dracula battle is stated to take place in 1792 and that the game starts 4 years later.Dracula, The Undead - [1897]
Bloodlines - [1917], some unknown time after the beginning of World War I.
If You take the stories of the CV games as presented in both their manuals and in-game text up to this point there is a reasonable timeline that fits well enough with the 100 year resurrection mythos. And there is basically nothing to support or deny the possibility the AjDen was intended to come after DDen.
However, I will bring up something that you didn't; Ralph C. Belmont. It is common for a child to have a middle name derived from a parent or grandparent. So Ralph's name could be another indication of intent, but again it is not supported by anything concrete. You would have to make an assumption that Ralph's middle name came from Chris, or that Chris was named after Ralph's middle name. So we are really just back to square 1. We really just don't know enough to say anything for sure.