Iknow guys make over $10k per day from facebook, I know guy make over $10k per day from SEO with adsense! and I know guys who make over $10k per day from media buy. So it does not make sense to talk about which is the best method. Think about which is the best method you like and you are good at. For any promotion methods, you can make enough money. For sure you need to spend enough time into research and test. Focus is the key to success!
Personally I am doing article marketing and it is good money as well.