Any TV with "120 Hz" uses interpolation to fill in the extra frames. This induces MAJOR input lag [delay] into the system, which makes most current TV's unsutable for gaming. [For example, the newest TV's from LG and Samsung have been measured at over 100ms input lag on some models!]. Furthermore, they are incapable of using a 120Hz INPUT signal, meaning they can not be used for 3d.
Typically, "240 Hz" TV's operate in teh same exact manner, but can actually recieve a 120Hz Input signal, making those 3d capable.
In any case, for gaming, any image interpolation should be disabled due to the extra lag time that is introduced into the system.