Battletoads was unbelievably difficult
It was fun, but not exactly a prime example of how games should be made.
There's one reason and one reason only that Rare games become cult classics... It has to do with when they come out and the innovative, new-for-its-time features they add.
Battletoads- Pushed NES graphics to the max.
Donkey Kong Country- Prerendered graphics.
Banjo Kazooie- ... Honestly this game was just plain ol' good. Didn't need much innovation.
Banjo Tooie- If Banjo Kazooie hadn't come out, this game would be overshadowed.
Conkers Bad Fur Day- Rated M on N64.
Goldeneye- One of the first console shooters with decent multiplayer options...
Perfect Dark- Only really popular because it's built off of Goldeneye's engine, without the James Bond brand, and was hyped up as such.
For the most part, those games are generic with the exception of what I listed. Nothing really amazing about any of them outside of "they came out at a time when their features weren't common". If any of them had come out today and never existed in the past, you would overlook them much the same as you are Rare's current games.