i say the NFS series.
I've played MC3 and Juiced as well but NFSMW gets 1st place.
Juiced was good for crashinf (cause of the damage models)
MC3 was exactly like MC2, but with new cities and liscensed cars.
I got a 74% savegame that I stopped playing.
100% parts unlocked
LV 3 Nissan 240SX
100% win so far
all unique parts except for widebody kit (U need to do 1 more outrun race to unlock it)
1 more race until finished with career mode
I have another one with a Lv3 H2 as well