Rating this is hard. This came out at the perfect time for me when I was madly in love with this type of game (actually, I probably still am, but it's just something that crops up often anymore sadly). I know some people aren't a fan of the concept of ridiculous collect-a-thons, but I really enjoy the satisfaction that comes from completing such a task, and there is sooooooo much of that in this game.
However, I have problems too. When comparing this to its common counterparts in Super Mario 64 or Banjo-Kazooie, I find that there's a certain level of depth missing in this one which shows in multiple playthroughs. While the other two have a general focus of 'get here, complete puzzle', this is more a case of 'get here with correct character; instant Golden Banana'. I have to stress the correct character part because that results in the most tedious backtracking ever. But yes, there are some puzzling elements in the later levels, and my first playthrough of the last level was exhilerating, a lot of it, especially in the first levels is just hitting switches and beating time limits, which isn't exceedingly exciting. The true enjoyment comes from playing the more unique puzzles. The same thing goes for the minigames. Some of them are repeated far too many times (it's fortunate that I've finally become adept at "Beaver Bother", but I still hate it), some of the more rare ones are a delight, especially anything that involves a minecart.
Again comparing it to the other two games, there's just something lacking in the combat with this. I feel with Super Mario 64 in particular, the enemies you come across feel like obstacles, and part of the level to tackle. In Donkey Kong 64, they're more like mild annoyances that are either too easy to defeat, or too tedious to bother with, especially since they respawn too quickly. The bosses on the other hand, are a delight. Although there are a couple I've gotten too sick of from overplaying (Jack-In-The-Box thing), and there's still the frightening one that I hate (Cardboard Cutout thing), the other ones are fun, especially the final battle at the end, which balances a variety of gameplay with pure charm. It's been at least a decade since I've played a proper, competitive game of multiplayer, but I found like many other Rare games at the time (Jet Force Gemini in particular), there's something missing in it, even though it should work in theory. I think part of the problem is that it just turns into a game of search and then a battle that inevitably stalemates unless someone has homing weapons or a third or fourth person gets involved. For that reason, I think the arena multiplayer mode is much more playable, and has the spontaneity that multiplayer modes need.
My mixed opinions above are why I find this difficult to rate. On one hand, this is somewhat flawed in comparison to similar games that I'd rather play, but on the other hand, there's always that part of me that wants to collect thousands upon thousands of items, and this is what pushes it up to a 5 for me.