The Need for Speed franchise has been around for a long time. Starting back in 94 with Need for Speed and pushing all the way to today's Shift and Nitro, the brand is definitely a strong one. While some of the games may have been sub par (I'm looking at you ProStreet and Undercover) others have been amazing (Most Wanted, Carbon, etc.). Regardless of whether you like the series or not, there are people out there who do, and thanks to them, 100 million units of Need for Speed games have been sold to date.
That's a pretty big feat, especially spanning 15 games over 15 years. Most franchises die out within the first couple years but NFS has pressed on. For a game to be released almost every year with enough pizazz to warrant a purchase from the previous year's faithfuls says a lot about a game. And as I said, there were some crappy ones in there, but 100 million is a huge number. Congrats Need for Speed. You've earned it.