I am certain that nuclear power takes days to "spin up," so even if gas plants are not responsive (it is my impression that they are), it is still sensible to compare them.

The real reason to consider nuclear is that there is more than construction cost, there is also fuel cost. The fuel over the life of the nuclear plant is considerably cheaper than for a gas plant. Of course, even that isn't the whole story: I don't know how total operating cost and negative externalities balance out.

EDIT: I misread; it appears that those numbers are total cost per MWh produced, not construction cost. In that case, it appears that gas definitely beats nuclear hands down (ignoring the CO2 problem).