From the start of the game it's pretty clear Rayman 3 is primarily an action game.  It is a platformer, but only because of the way the levels are designed.  The rest of the game has more in common with Tomb Raider than Mario (minus the weapons and frequent tomb-raiding).

Enemy encounters are pretty frequent.  Most can be easily defeated by throwing your fists at them (sort of like a boomerang that comes back every time).  Others might require a little more thinking from the player, since some enemies can only be hit in certain spots.  Overall the enemies aren't too difficult, but the greater amount of them makes it much easier to die, especially when trying to get across a guarded platform.  One wrong move and the enemy will hit Rayman; he'll then be thrown back a little and fall to his death.  Situations like these are actually a little trickier the boss battles, which require more patience and timing than skill.

Rayman 3's level structure is much better than the GBA port of the original, but it lacks originality.  Each world has a number of stages to explore, all of which feel like a repeat of the one before it.  The worlds are different, but the stages within each world are all too similar.  The mini-game stages are somewhat unique, but the main stages are very repetitive.  You'll see the same object, the same platform and the same area to climb over and over again.  Some might be a little higher, or a little bigger than the previous ones, but it still feels like you're experiencing deja vu.  That would be Rayman 3's greatest flaw.  It's hard to believe that the first game in the series, which was developed several years ago, had more variety.

Looking past that flaw, Rayman 3 is a good platformer.  The camera isn't as confusing, so the levels are easier to navigate.  To be honest, I enjoyed this game more than the original.  The original was more polished in some areas, but this one is more fun.

Rayman 3's visuals are both impressive and not-so-impressive.  What do you get when you have repetitive level designs?  Repetitive backgrounds.  Your eyes will grow tired of looking at the same thing for 20 minutes, and wish that the game looked as good as the animation.  Rayman moves very fluidly.  Smooth, detailed textures give Rayman an almost three-dimensional look.  And as expected, all of Rayman's foes are animated just as well.  The other effects (various liquids, fire, smoke, etc.) vary in graphic quality, but for the most part they fit in with the game's higher-quality visual attributes.

Fans of the previous games will definitely want to give Rayman 3 a shot, but I'd suggest holding off on a purchase.  There's a lot of fun to be had with it, but it is very short and fairly easy; most of the levels can be conquered within a matter of minutes.  Death is not a problem, since you are allowed to continue as much as you want.  And earning extra lives is as easy as playing through an easy stage a few extra times.  Still, Rayman 3 managed to keep me glued to my Game Boy Advance, and that says a lot considering how many flaws it has.  I'm glad I had the pleasure of playing through the first Rayman game developed specifically for the Game Boy Advance, and I'm sure you will too.  Just don't be too hasty to buy it if it isn't on sale.

Gameplay: 7.5
This was a hard choice to make.  On one hand, Rayman 3 is worthy of an 8.5.  On the other, it has a lot of flaws that are impossible to overlook.  This is not a port, and among all of the platformers developed specifically for Game Boy Advance, Rayman 3 is one of the best.

Graphics: 7.9 
Rayman 3 was so close to receiving an 8, and would have probably received a 9 if it hadn't been for all of the repetitive imagery.  Having great character animation isn't enough, but this game stands as one of the best-looking GBA games out there.

Sound: 6.5
Wacky music and silly sound effects are all you'll get out of Rayman 3.  The soundtrack is well-composed, I just don't like that type of music.

Difficulty: Easy
It could be argued that some parts of the game are challenging, and that other parts are downright frustrating, but the tasks that await players of this game are ones that we all have faced before.  Unless you aren't old enough to remember the days of the SNES, Rayman 3 will be easy to complete.

Concept: 6 
Rayman 3 is an improvement over the original in that it’s more fun, but other than that, very little has changed.

Multiplayer: 6.9
Rayman 3's multiplayer mode is a good time-killer, but it's not as exciting as the multiplayer mini-games created for the console versions.

Overall: 7.5
This is one of those "it could have been a must-buy if..." types of games.  It's a must-play, but only at an affordable price (that is, as a rental).  I enjoyed it, and I want to play through it again, which proves it has some replay value.