I never really minded the idea of Mathias, but it wasn't executed that well. We hear about him in the beginning, never hear from him again, so his betrayal is EXTREMELY easy to guess from a mile away.
I just remember when I first started to play CV4 when I was young, and how its more realistic and adult theme pulled me in. I remember the back story, and assumed the Belmonts have caught Drac for hundreds and hundreds of years (His unspeakable actions were consistently thwarted by the Belmont family), and how I wanted to learn and k ow about those other confrontations, yet loved the mystery and unknown history.
I like to say:
Legends
CV3
Adventure
Belmonts Revenge
CV4
Simons Quest
Dracula X
SOTN
OoE
CotM
LoD
CV64
Bloodlines
PoR
Julius game that we should be gotten lol
Aria
Dawn
And even after that, I just wish it was Drac vs Belmonts from like LoI time and every century, because I love me some Belmont vs Drac action, but as games started to require heavier stories, CV had to follow (hence some cheesiness in the CV plots like in CV64's Reinhardt Rosa love story).