If you want to be real technical about it, there are only three different "Draculas" in the different versions of the CV storyline: Vlad Dracula, and then Gabriel Belmont and Mathias Cronqvist. From the first Castlevania game all the way up to the N64 titles, Dracula is obviously the real deal, Vlad Dracula. And until the change in LoI, the games heavily drew on Dracula's historical background. For example, at the end of Simon's Quest, you see Dracula's tombstone, and it reads "1431-1476." These are the actual birth and death dates of the historical Vlad Dracula. And by the way, Dracula was not a nickname. "Tepes", or "Impaler" was the nickname, and only given to him after his death. He also signed his name "Dracula." Copies of his signature still exist. Also, in Castlevania III: Dracula's Curse, the game takes place in 1476, which would be the year Dracula died, hence, the same exact time he would have become a vampire.
And Castlevania Bloodlines finally made the Bram Stoker novel "Dracula" part of the canon, and in that book, Dracula is clearly an undead Vlad. Van Helsing makes this abundantly clear in chapter 18 when he says "He must, indeed, have been that Voivode Dracula who won his name against the Turk, over the great river on the very frontier of Turkeyland. If it be so, then was he no common man, for in that time, and for centuries after, he was spoken of as the cleverest and the most cunning, as well as the bravest of the sons of the 'land beyond the forest.' That mighty brain and that iron resolution went with him to his grave, and are even now arrayed against us."
Personally, I'm not really a fan of the direction the series went with making Dracula into someone else, who, well, wasn't REALLY Dracula, but just happened to take that name at a later date. So for me, classic Dracula is the only real "Dracula."