I never had sonic adventure before and this game is actually not too bad.
The graphics aren't at it's best standard although it has been taken off the Dreamcast They COULD of improved the graphics and edited the graphical glitches. When the blue hedgehog himself talks he looks like he is shouting at a naughty child at school. My tip for them is to make the graphics up to sonic heroes standard.
The music is mostly remixed from zone's on sonic 3d which is well, not bad plus the singing on knuckles just sounds weird when it gets high pitch and it is better off with just the rapping, So look out for that one. The normal sounds are taken out of the previous sonic games and they twitched small faulties to make it sound proper. There is the regular jump and ring collecting sound, But when you are playing with knuckles and you come out of speed highway: jump over the left wall and a strange sound will happen. (You will also see a gate shutting on the jewelry shop).
Overall great game and there is a few parts of the game which should of been edited. If I was you I would rent it first to see if it is up to the standard you will like it to be.