I really did enjoy Conker's Bad Fur Day...
- It had the right difficulty
- It's Multiplayer was memorable
- And so much profanity made it hillarious
- Simple story... Conker has a hangover, he gets lost... he's just trying to find a way back home
Then you got stuff like Goldeneye, Mario 64, Super Smash Bros, Banjo Kazooie/Tooie, (And OoT and Majora's). which is all indeed a core of their own...
It's really hard to base a title of best, when you have so many good titles...
Personally Conker's BFD was my favorite, The deathmatch was almost too fun to play...
I can't really state a best, N64 really did have an amazing run in it's console war era...