A visual feast
Most obviously is the graphical style. I don't know if this was the first game to use cel shading, but it was the first I played that used it. Every part of Tokyo-to is stunningly realised in a cartoony style. No part of the town is shoddily done, every part has been taken time over, and this extends to other aspects of the game.
The idea of graffiti hadn't been tackled before in a game, at least in this sense, where you are actually doing the graffiti. This was a brave move from Sega, and even got them in trouble when they held a graffiti contest to promote the game.
The music was perfectly selected, supporting the game at all times with tunes that you just had to tap your feet to. The characters voices were all well done too, especially DJ professor K, who expanded the story at several points, including many bizarre references to personal hygiene.
Finally the noise that the police make while they chase you, I'll always remember 'hup hup hup hup hup hup hup'
The fact that you didn't choose which trick you would perform each time you jumped, or attempted to grind a rail. Perhaps this would've detracted from the overall game experience, as it was mainly about the graffiti and avoiding the law.
The Bottom Line
A very brave and individual game. The cel shaded graphics put this game in a league of it's own, if you find this game cheap I seriously recommend you buy it over it's X-Box sequel, Jet Set Radio Future.