My personal favourite is need for speed most wanted, but it came out around 4 years ago. So there are newer versions available now. I am giving a brief description to each one
**** 2009 : Need for Speed Shift
simulation racing on tracks, greater respect towards physics :D
more real handling, going to be released soon
**** 2008 : Need for Speed Undercover
arcade racing game, street racing, cop pursuits, jobs, you play as a undercover agent. Quite predictable story line, not much customization of the cars.
**** 2007 : Need for Speed Prostreet
Even a die hard need for speed fan like me would say that prostreet sucks. Took out the arcade racing part completely. You race on tracks. Boring all the way through. I didn't bother playing it the 2nd time. I have completed rest others atleast thrice
**** 2006 : Need for Speed Carbon
racing in the night, has some new races like the canyon ( i really liked that one), the drift races were back after mysteriously being left out in most wanted, there are pursuits but they aren't compulsory, boss races, crew members (they are a lot of help in the races and you can customize their cars too).Much shorter that its predecessor
**** 2005 : Need for Speed Most Wanted
My personal favourite, and i can bet of everyone else's too who has played it. Police pursuits were back after the two underground editions, The police were intelligent than their hot pursuit 2 counterparts. The story line was good, and the black list always made sure that you had something to fight (race) against, pursuits were necessary, and were one of the most enjoyable part of most wanted. I just can't stop writing about this masterpiece. After this game all the iterations of the need for speed series faced the same question " Why is this so unlike NFS MW?"
So i would say most wanted, but you can give others a try as the graphics have seriously improved much over the past few years and so do have the capabilities of the video cards currently installed on the gaming monsters (consoles). Now that you have got a fair bit of idea over all the games, you choose yourself which one you go for. The versions prior to most wanted have been skipped. If you want them or have any further questions then feel free to mail me at pb_virus@hotmail.com.