That’s the beauty of NFS series, I believe! It has so many entries across different sub-genres of racing game. You know, come to think of it, it’s like a beautiful accident. If it wasn’t EA forcing Black Box to release the half-baked Undercover, we wouldn’t have the period of SMS and Criterion helping to develop non-Black Box NFS games.
I have to admit, though, I am as much unfamiliar with both Shift games as classic NFS games prior to Underground. Bought Shift when it was discounted on Origin (but never once played it), and giving up Unleashed when stuck with the first 240SX drift event. I guess that was the point when I decided to stick with games focusing on street racing and police chase.
I do like MW 2012, it has a great variety of cars (with unusual presents of SUVs and track toys), great visuals, on-spot car sounds, and crazy police chases, etc. It even has performance upgrades that can be equipped during race and pursuit! Though I get the idea of it resembling Burnout: Paradise too much, and its little sense of progression in singleplayer, I still enjoy the game very much!