While the classic Sonics' have always been about fleet footed excitement, the Sonic Adventure series has chosen to put is emphasis on the adventure portion. Sega has toned this down a bit in SA2 by removing the hub areas from the first release and making the adventure more of a traditional level-cut scene-level design but now they have added the adventure during the actual levels. Players can choose to play on either the Shadow or Hero side. The Hero side included Sonic, Tails and Knuckles while the Dark Side has Shadow, Rouge and Eggman (Hey, when did Robotnik revert to his Japanese Eggman name?).
The best part of SA2 is the Sonic/Shadow levels, which run at an accelerated pace with plenty of loops, leaps and ledges that ARE sonic. If the entire game was like this, this title could have easily been on of the best Dreamcast games, but the Sonic levels are only 1/3 of the adventure. The other 2/3's include the Eggman/Tails levels, which are essentially a Panzer Dragoon type shooter; slower paced but still moderately entertaining. The final set of Knuckles/Rogue levels can be excruciating. They move at a snail's pace, with the player "hunting" for what seems like an eternity. I found myself only playing through them to get to the next Sonic level. That is never a good sign.
What is really odd is that after besting SA2, you get the option to play the original green hill zone from Sonic 1, now in totally luscious 3-D. Since this is the hidden treasure for completely beating the game, it looks like Sonic Teams still knows what we want. Too bad the entire game wasn't like this.