Some of the replies would appear to suggest that nobody should travel with Ryanair and as pointed out, the basis of "you didn't pay much" is specious.
On the basis of their terms and conditions, Ryanair might take you if they feel like it but there again they might change their minds. I am surprised that anyone can actually condone allowing people to check in i.e. accepting them for the flight then informing them that the flight is cancelled.
Does anyone have the real reason why the flight was canceled other than it was delayed and therefore easier to cancel than to operate.