An enjoyable platformer
The cages are still in Rayman 3, but not only are there far fewer (50, versus over 100 in Advance) it's not even necessary to find them all in order to progress. Add to that the fact that they're not hidden in ways that require ridiculous amounts of searching and trial and error, I found I actually wanted to find all of the cages in the game.
The gameplay can be occasionally frustrating, especially when you lose all your lives and you have to start a stage from the beginning even if you got a checkpoint, but I found it far more enjoyable overall than the gameplay in Advance. I do wish all platformers would go the route of the Jak and Ratchet and Clank games and do away with this ridiculous arcade concept of limited lives. It's good if you want players to keep pouring quarters into your machine, but on home consoles it's just an annoying artificial level of difficulty.
On top of the cages, the game also allows you to collect gold lums (1000 in the game). Finding all the lums in the levels in a particular world unlocks an extra bonus stage so there is a reward for finding them all. Though some are hidden, anyone who takes their time, and makes sure to backtrack when they receive new abilities probably won't have a whole heck of a lot of trouble finding all the lums in the game.
Though you do need to play certain levels in order to collect enough cages to move onwards or to receive special abilities required to reach new levels there are several levels in the game that you never even need to play. These are the special 3D stages where you either get pulled along behind a sea monster through a swamp or drive a go-kart through a lava field.
Rayman 3 is pretty short, and it didn't take me very long to play through the whole thing and find all 1000 lums and 50 cages, but if you enjoy platformers then I would have to recommend this game.