The worlds and levels that Sonic, Tails, Knuckles and Amy Rose must travel through are filled with many highly detailed obstacles and objects. The detail put into the game's graphics were definitely above par. They weren't the typical blocky models and scenery that has become common on the GameCube.
One aspect of Sonic Adventure that really impressed me was the music. It wasn't the basic bells and whistles that I have come to expect from some games, but the music in Sonic DX fit the levels and was of high quality. For example, the first time I traveled to The Mystic Ruins, I was shocked to hear a lot of percussion and chanting that made me feel like I was at some ancient temple deep in a South American jungle. The sound was a big plus for me. In most games, I found that I could play without the music and not have any problems, but this was the first game in a long while that made me want to turn up the sound.