I can't prove it but even though on the xbox360 games say they are 1080p, I don't think any of the games are true 1080p, they have just been upscaled from 720p. I have a few of the same games on xbox and PC and non of the xbox versions have the same clarity as their PC counterpart. I believe that if a game is running at a lower resolution, the smoothness of the game (frames per second) will appear to feel smoother compared to a game running at a higher resolution.
Frampa makes a good point too, which is when locking your FPS using any software such as DxTory (which I class as 'artifical') or driver based using nVidia inspector to say 30fps, but your system is capable of pumping out much more then that, then this some how makes a negative affect to how smooth the game is. BUT when you can lock the framerate on an application or software level, such as Crysis 2 with the console command: 'sysmaxfps = 30' (if I'm not mistaken) then the game is only rendering 30 frames and not having to drop any wasted frames, thus not creating any negative affect. By negative affect I mean this:
Try this experiment for yourselves: You'll need a controller for this. Boot up a game which you can run smoothly at 60fps. when your in the game, just turn the camera slowly using the controller joystick. Providing you can run it at a constant 60fps, it should be silky smooth. Exit the game then which ever way you use to limit your framerate, limit it to just 59 frames, then boot the game back up. Once in the game again turn the camera slowly and pay close attention to how smooth it is. If you have a sharp eye you will notice that about every second you will see a tiny tiny skip in the camera movement. I feel that because you've capped your framerate which is a frame lower then your monitors refresh rate (most monitors are typically 60hz I should have mentioned this before) it has to drop this one frame creating the tiny skip. However many people cap their framerate 1 frame lower then their monitor to reduce v-sync lag, which is a whole other issue, which is what I do with most games.
i feel like you just nailed it there bro thats exactly how it is, and yes ive noticed how it skipps when even capped at 59fps or isnt smooth like 60, well 60 isnt smooth for me but thats another dirty little skyrim issue thats been giving me a headache from day one aka 64hz, but yeah, what you said is exactly what im talkin about, it seems the lower you go the more it sort of catches as you rotate the camera slowly at 30 if you move the camera around slowly it seems like its actualy being pulled back or something, hard to explain. just not smooth like console, and it also makes scense as well about the fact that your using third party to cap the fps, like its not really meant to be done, like your holding it back.