The folks at Oculus have done some good research on this, they found out that generally people find it hard to spot any difference in frame rate after 90fps.
Your monitor is probably using something between 60 Hz to 75 Hz. Do you see any flicker on it? Peripheral vision is more sensitive to flicker, so also try looking off-angle. This also depends on whether it's CRT or LCD.
There are TVs claiming to use much higher frame rates. Well, for one, they still use a lower frame rate, just use higher blanking period since that reduces motion blur, and they call this higher frame rate [1]. This motion blur however is due to slow response of the LCD though.
[1] As am example, a TV using 120 Hz frame rate which puts the actual frame only for 50% of the frame time would often be advertized as a TV with 240 Hz frame rate (without telling you that every alternate frame is a black image).