I had both of these games and my advice is to do what i did and sell them both.
COD2, i beat it on normal as well, and i don't know if your like me or not. But once i beat a game thats it no more single player. I won't go back and play the same game again on a more difficult level, to me thats boring. The multiplaye is good, but laggy and only 8 players is not what you should expect from a next-gen game. I sold both and got GRAW, after this game you will NEVER go back to COD2.The graphics alone in GRAW make COD2 look 1st gen (no joke) (COD2 is awesome game, but nothinig compared to GRAW)
NFS MW, i found i just stopped playing this game.... so i sold it and preordered BF2 MC
Just my 2 cents. think to yourself, if you keep these games, will you honestly play them later on? If so then keep the game your most likely to play, otherwise ditch them both (if you can)