Banjo-Kazooie is just one of those games that justifies having a Nintendo 64.
Banjo-Kazooie has a fairly basic story that involves a kidnapping of Banjo's sister by the witch Gruntilda, so that she can steal her beauty. As Banjo and his feathery buddy Kazooie, you explore Gruntilda's lair and collect jigsaw pieces to complete puzzles. Each puzzle opens into an area that has a unique theme and is a completely new experience. These areas are often very large and the opening is quite far from the level entrance.
Banjo, the bear, has a few basic moves that he can use to explore the world, such as punching and jumping. By using more complicated actions, Banjo can utilize his friend Kazooie, the bird in his backpack, to pound the ground, shoot eggs, and eventually fly. You learn moves and gain the ability to use special items as the game progresses, and usually they are given to you just before you need them to get to the next area, or to go back to the previous area and find a jigsaw piece.
Banjo-Kazooie has taken the Super Mario 64 formula and greatly expanded upon it. The overworld is much, much larger. Each of the nine levels in Banjo-Kazooie contains 10 jigsaw pieces, one of which is found by collecting the five hidden birds called Jingos, and 100 notes, which are used to open specific doors by having at least the number of notes on the door. The overworld has a few shortcuts that are opened by finding two of the same color cauldrons; these greatly decrease traveling time between some of the areas.
The graphics in Banjo-Kazooie are very much more detailed than in Super Mario 64. They feature textured surfaces compared to Mario's shaded polygon approach. The soundtrack is very catchy and you may find yourself humming along to the themes once you start to play them a little while.
If you happened to enjoy Super Mario 64, you owe it to yourself to check out Banjo-Kazooie, even if it is just to see how great some Mario clones can be.