It depends on the airline, but you'll pay twice as much for 1st class than you will for business class. With the better airlines, both business and 1st class have seats that fold down into beds, but the 1st class seats will be larger and often your own "suite.". Airlines like Cathay Pacific will give you designer pajamas and amenity kits, access to 1st class lounges, better food and the finest champagnes, wines and liquors.
Business class is not bad though, you'll still have beds on many airlines, much better food than economy class, designer amenity kits, priority check-in, boarding and baggage handling and access to business class lounges before your flights.
Check out the difference between Cathay Pacific's 1st and business class seats, then check out the price difference. Business class is just fine in most cases:
http://www.cathaypacific.com/cpa/en_INTL/whatonboard/newfirstclass