what response time is better - 5 ms or 2 ms?

Surprisingly, you can't tell from just numbers. Some monitor manufacturers give response time in white to black changes, while some give them in grey to different grey levels, while some give them in white to black to white level changes. The slowest changes on an LCD are grey to grey, so manufacturers who give times that way will *appear* slower than manufacturers who give white to black speeds. Generally speaking, even though grey to grey speeds will be higher, and make a manufacturer's LCD look slower, if you are looking at a grey to grey measure LCD then you are probably dealing with one of the better LCD manufacturers and will be better off with the grey to grey measured display rather than a white to black measured display.

Realistically, by any measurement spec, a rating below 8 ms will be sufficient for almost any user, whether for typical desktop usage or for gaming. For anyone who would not find either of the rated speeds you listed sufficient, they would also know what the numbers mean and how to find which rating method the manufacturer uses. That leads me to suggest that for you, whatever LCDs you are looking at with those rated times will be fine for your needs.

2 ms is a better response time. The bigger the number, the longer it takes. In lcd's the higher the number, the more 'ghosting' you can see.

2ms

2ms

Faster is better.