I enjoy playing two types of games, FPS and racing sims.
What i've found with these are that while the FFS single player can be enjoyable the AI is very predictable. I completed MW2 on the hardest level recently and when I got stuck on a certain section I found it didn't take long to work out the AI of the enemy to clear the section. Even on that level it only took me about 6 hours.
I recently bought F1 2010 too and while there are flaws in the development of the game I have found the career mode to be the most challenging I have ever experienced in gaming. The concentration required to complete a full race without falling off the track is very high, well for me anyway, which adds to the tension and enjoyment.
What i have also found the online experience is so different with these two types of games.
The online gaming is more playable with FPS than with racing sims.
I'm online all the time with COD but I never play online with racing sims. I have tried but each race is the same. Flat out out he straight brake, get shunted off by some idiot behind. Over take get shunted off again at the next corner. Repeat til end.