My favorite N64 games are Wave Race 64 and Diddy Kong Racing, followed closely by Super Mario 64!
I’ve also grown to like the first Castlevania a bit, but it’s ugly as sin and definitely an acquired taste. I played very little of Legacy of Darkness but it’s supposed to be better, so perhaps that’s the way to go (if at all...).
I...really didn't like Paper Mario that much, which is strange since I liked most of the other ones that came out. I think at the time I was still starving for a direct sequel to Mario RPG, so maybe that corrupted my expectations.
The Goemon games you should definitely play. I'd also argue for Bomberman 64 - the multiplayer is fairly meh but the single player campaign is a lot of fun.
Hey, if you were/are into Paper Mario more power to you. I really wish I enjoyed it more. Part of me wants to go back and see if I'd enjoy it more these days now that I've come to terms with the fact there won't be a direct sequel to Mario RPG.
That said, I LOVED Thousand Year Door and I actually really enjoyed Super Paper Mario.
I liked SPM too, but TDD gets major demerits for sticking an overly long and unskippable cutscene in the middle of the final boss fight. It's so great overall, but I could never stomach sitting through it repeatedly so I've had it sitting unfinished for nearly 15 years.