The people who like the N64 games are a VERY vocal minority. Members of this camp will rant and pout enough to make you believe the games were actually liked, if not loved.
The truth, however, is the N64 titles are abysmal in nearly every gamer's eye. They were critical failures, getting blasted by nearly every publication. Konami will never re-release them. Developers like IGA actually APOLOGIZED to the fans, and asked us to forget they existed. This all sums up the company's attitude toward them.
What they did right:
Unique multiple characters
Atmosphere
Good level design with actual platforms
Nice set of movement abilities abilities; like slide, and climb
Story was a bit more in depth than usual CV titles
What it did wrong:
God awful camera, and no LoD didn't help it that much
Slow, clunky, unresponsive, nearly unplayable controls
Combat unsuited for 3D environments
Having to stop and pickup every item on the play field (like, subweapon ammo), slowing down your progress and flow
Music was nearly non-existent and lack luster (more opinion orientated)
Graphics were shitty (more opinion orientated)(I personally think it looked fine for N64)
Many CV64/LoD proponents will argue "But like it had so much potential man!" and "Look at the prototype! It had way more stuff!" Well that doesn't mean shit if the actual game didn't have it. It is not a positive point, in fact the developer's failure to complete it all is a negative point.
Despite all of it's good points, a game mainly comes down to gameplay and play-ability. This was where they fell apart the most, and earned their place as some of the most unpopular Castlevanias of all time.