In order of how much I like the follow ups to the original series:
1) Knight Rider (2008)
2) Knight Rider 2000
3) Team Knight Rider
4) Knight Rider 2010
KR 2008 has done a lot to connect itself with the original series, and I give it a lot of credit for doing that considering it's 25 years later and the last two shows to receive this treatment were complete reimaginings (BSG and BW).
KR 2000 had great intentions, but fell flat in execution. The best parts are Michael's interactions with KITT and KITT getting the new KIFT body. The rest was...blah. KITT spent way too much time in a non-super car body for the flick to be interesting.
TKR is, IMO, the series that came closest in tone to the 80's series with its cheese factor. However, it's tough to write a good relationship between one man and his car, no less five individuals with their vehicles. Also, the exteriors of the cars really weren't distinctive in any way and the acting was rather bland. What I give major kudos to is the writing staff's intention to work in the history of KR into their story arc and the inclusion of elements such as FLAG from the get go.
KR 2010 is much reviled, and with good reason. However, I enjoy it as weird B-movie fun. It had great ideas, it just excecuted them badly. I like the use of a "western scifi" setting and I enjoyed the new car being a customized Mad Max style vehicle. I even dug the storyline where Hannah's consciousness becomes the car's "AI". Everything else fell flat for me.
What saddens me about KR 2010 especially is that it was meant to be a much different movie initially. The original script involved every state having their own "super car", with FLAG having formed what amounted to a large scale private police force hired by the government. The story would have focused on the one for California being destroyed and its replacement. The only element that remained from the original script was the use of a woman's mind as the AI of the car. The original script included references to FLAG, KITT and Wilton Knight. I suspect this change was due to some of the Glen A. Larson wrangling over KR rights back in the day.