The sole reason that Sega should still be producing the Dreamcast
Gameplay: Rayman 2 throws enough surprises at you to keep the game interesting the whole way through. Sometimes, certain elements are repeated, most notably the surfing ones, but the locales and situations they take place in always make them a fun and interesting diversion from the normal action-adventure gameplay. Battles are slightly awkward and easy, and your enemies are, for the most part, the exact same; robot pirates. They get more health and get more powerful weapons later on, but it's the same "dodge, charge-up, throw fist, dodge, charge, wait for enemy to be hittable, throw fist" formula. Boss battles, on the other hand, are always creative and interesting, not to mention challenging. The second boss, though, Umber, is one of the weirdest ones. You basically just swing onto his head, and he carries you to a ledge while sinking into lava. It's an odd battle, but the next one, Foutch, makes up for this lame-duck of a battle with Umber. With Foutch, you have to navigate in a little maze of a bridge while Foutch throws walls of fire at you, which is only difficult enough to not be frustrating.
The camera in this game can be a bit odd. For most of the game, you have a 3rd-person view, and sometimes that is the most annoying view. The camera refuses to go around or through objects when trying to get around you, so you are occasionally forced to make a blind jump or something. When it switches to an "environment" camera, it's in a fixed place, and it's usually in a good place, too. It's never too sudden to make you switch the way you're holding a thumbstick; it always transitions nicely and offers a good view of where you should be going and what you should be doing.
Graphics: This game has better graphics than some games nowadays have. The fact that it looks amazing, even after 6 years, should give you a visual of how good this looks. Character models are bouncy and expressive, especially Clark, who, when he looks excited, gives a really toothy grin that looks goofy to the point where you just can't help but smile at the first time.
Underwater environments look positively amazing in this. Everything is blue and aqua themed, and there's plenty of flora. Every single environment; jungle, bayou, marsh, underwater, beach, volcano, cave, pirate ship; look amazing and unique. The lighting is great and it really immerses you. It doesn't look perfect, however. Certain graphics in this, like a pit of thorns, are usually shown with a 2d animated texture, and that can look awkward, especially from certain angles where it's clear that it isn't really thorns, but just a texture.
Sound: Another high-point of this game is its sound and music. The music is usually not repeated, but even if it was, it's good enough to where you'd welcome listening to it again. The soundtrack of Rayman 2 is astounding, and really helps you immerse yourself into the game. Boss fights have music that sounds appropriately epic and tense, while the underwater sub-level where you follow Carmen the whale sounds calming and, well, outstanding. The songs sound appropriate with their environments, too. For example, in the jungle levels, you'll hear laid-back beats with sort of jungle-y drums playing, while music in the bayou levels sounds very southern.
The sounds in this are fairly good, but when i say "sound", i also include voice-acting, which is probably the one thing that brought this down. The sounds are amazing: water splashes, surfing noises, explosions, Rayman's helicopter-hair....I could go on for a while. Explosions sound especially good, as they are short and powerful-sounding. It's hard to convey the sound in text, though. You just have to play it so you can hear this symphony of sound in your ears.
Voice-acting, though, is another story. My only problem is that it's all in gibberish, and often repeated, especially for Rayman. You'd think Ubisoft could have recorded different sounds for Rayman's dialog, as you would with English, but his little spouted gibberish sounds are repeated a multitude of times throughout the game.
Value: I played this game for 5 years. Who would say that isn't good value? It's more fun and addictive than most games nowadays, even on a discontinued and somewhat out-dated console. That makes this game valuable, in my opinion.
Overall: This game is an amazing experience that really just transcends normal gaming boundaries, and includes many types of gameplay in it. Puzzles are interesting and appropriately hard, but never frustrating. If you have a Dreamcast, you need to get a copy of this, immediately.