NFSU2 was the best, only liked Most Wanted cause it took me the longest to beat. Beat Carbon in one day, prefered the drifting style in NFSU2 better cause I controlled the drift instead of carbon where they do it for u, it's too easy. Didn't have any honda's in carbon so I had to go with the EVO.
Don't know if anyone else reads the actual articles on the games but I found it amusing when they were making Most Wanted they said it has nothing to do with NFSU and is not part 3 and said the same thing when they first started on Carbon but somehow they ended up tying all the story lines together.