However, cruise would give you a very basic first impression and then you can choose what interest you most and plan for a land trip.
Given it to me, I would not do Europe by cruise, except for the Baltic/Scandinavia, may be Greece.
The ideal way to enjoy France/Italy/Spain, is to drive. Next to it, is by train. Next to it, fly the LCC.
One only needs to look at the Continen's Map and would realize why land trip is a much better option.