I've lived in France and Spain, now back in the UK. Have also visited most of Europe on business or pleasure.
If language and relevant visas are no barrier, then France definitely has the best medical and social care, with family clinics, family allowances and good public schooling, but the worst record for strikes in the public sector.
Spain is less expensive than France, but medical care is not as good, there are no family allowances, and getting legal papers can be a long, frustrating hassle. But fresh food is more accessible, the weather is better, and there is an historical link with latino cultures. And the spaniards adore children - they just wont give you any help raising them!
UK - people are probably the most friendly here, but the cost of living is extortionate, the NHS a joke and the weather terrible. However, there seems to be less discrimination against foreign workers, as the UK is one of the most varied cultural environments in Europe.
Best of luck, wherever you go !