it all depends on how you like it and with what type of device you can cope. me, I am playing on a 2008 macbook pro without additional display and it works good :)
i use a 2ms / 75hz viewsonic and tbh its not that bad if you play in 800x600 or 1024x768 (with black bars on the sides).Its not CRT smoothness but i thought it would be way worse then it is.
I have a ViewSonic VX2268wm 22" 120 Hz TFT. I play Quake 3 and Co. with 800x600 @ 120 Hz in 4:3 mode. It's the same feeling as my 19" CRT! It played out super smooth and the picture is sharp (@ 800x600!). The monitor has no Inputlag. In short order, I sent in my crt pension.