Screen tearing isn't something you can solve with a 120Hz screen - I can promise you will get tearing in resource-intensive games on any larger-than-normal display, which is why you get V-Sync. This will limit the framerate to the native screen refresh rate though, meaning your graphics card will attempt to run the game at 120 FPS, probably killing your machine in the process (unless you have a superb GPU setup).
Once again: V-Sync synchronizes the vertical refresh rate from your GPU with the refresh rate from the display, so if you get a 120Hz display and you want to V-Sync a maxed-out Crysis 2 game, you're going to need a graphics card capable of running Crysis 2 at 120Hz, or you'll start lagging. Badly.
EDIT: Damn. Beaten by HEXiT. These ninja's...