I think asphalt 2 sucks, one of the worst racers for DS imo... same with ridge racer DS
I like the first asphalt urban GT, its got some nice drift mechanics, just don't expect too much from the game overall
if you want a well rounded racer, I'd go with need for speed carbon ds
and if you want one that will just punish you, go for NFSU2DS
I enjoy my racing games, good replay value in them and polish shows.
edit-
I really want a good racing game where it isn't always night time also, Asphalt Urban GT is as close as it's gotten.. and that was a launch game.. we should've had v-rally or something by now