I recently picked this game up since it was extremely top-of-mind when considering the greatest games ever made for the N64. For what it's worth, the game is capturing, but it doesn't come without a handful of flaws.
I believe that the strongest point of the game, undeniably, is the variety of Kongs to choose from and their dynamic personalities. This makes the game feel fresh and improves the longevity. In addition, the boss battles are creative, playful and fun - most notably King K. Rool, which I believe is one of the funnest boss battles in gaming history, using all of the Kongs combined to defeat him. The worlds are vibrant and colorful, making it an overall exciting environment, especially for '90s platforming.
The core mechanic of the game is simply running around collecting objects on the map (colored bananas, coins, soil patches, etc.). That wouldn't be all so bad if it only required the player to visit these areas once. However, to reach completion, the player has to run back and forth to the tag barrel to switch out characters to revisit each inch of the map several times. The game is very tedious at times and feels dry and lackluster, and drags to the point where a lot of it feels like grunt work. Finally, the game feels lonely at times, as it requires single missions for each individual Kong instead of using all of them as a team effort. The laboratory leading up to the final key was by far the best level of them all - it felt cohesive instead of exclusive, giving the player a sense of team pride.
Overall, Donkey Kong 64 is a very rewarding game undeniably worth playing, but beware of the substantial amount of tedious running around that this game entails.