Well i played a demo of NFS:Most wanted on Xbox and it kicks! I am going to get that game for the 360!
I would go SCIII, even though it wasn't that great a game in the end... I still can't get too into NFSU2 though, so I would naturally lean towards SCIII
soul calibur 3, i have it and it's extremely good, expect 1 part Story mode, can't skip scenes, but everything esle you have to do from scratch, even have a league mode(not online) that you have to win, you fight 8-9 fights against the toughest cp's and it scores you, there are 12 rounds so basically 12x8-9 is how many fights you have. Then there's Chronicle of the Sword, you'll understand if you get it. It has 20 missions and is pretty decent. Custom Charater's a remarkable, fix em up any way you want, you can even learn the same fighting style as reqular charater's. it's really good. Get Soul Calibur 3. Keep you intrested longer.
sould calibur 3 , you can never get bored of it , and the nfs:mw is great too and it will take u forever to get bored of it , so i have came to the conclusion that w/e ur choice is from these 2 games , you wont regret it
After playing both games , you will find SC3 more interesting. Theres much more features in it than the previous 2 titles. NFS is a decent driving game , should I say much better than most driving games nowadays. It all depends on how you feel. I would get SC3 though.