Here are some of the answers to your questions.
Which one is the best affiliate program to earn money online in terms of ad click naturally by the visitor, demand, good percentage income, payment
When it comes to earning point of view, very few affiliate programs are good enough for the bloggers and affiliate marketers. For example, Amazon has very high rate of clicks, the visitors also trust the brand more. However the revenue generation part is pretty steady and steep for the people who do affiliate marketing. The rate for Amazon affiliate program starts at 4% and grows upto 6% depending on the amount of sales being generated.
Flipkart on the other hand has higher conversion rates for the affiliate marketer. However on the trust factor, there are issues with the company. So often the flipkart clicks doesn't convert. But if it converts, the the payout becomes very high.
Ebay is extremely hard to monetize. And not only that but its one of the hardest program to get into for solo bloggers and affiliate marketers. Most of the coupon websites are easily eligible for the affiliate program.
The order in which people prefer e-commerce website is as follows - Amazon, flipkart, ebay, snapdeal, shoclues etc. So the conversion of the click has higher for the website in the given order.
Which one is the best compare between Amazon and Flipkart or eBay?
In order to compare these affiliate programs, you need to use your website or hubpages to test the strength of the click conversion from those programs. Prior to 2013, I have tested these 3 affiliate programs on Hubpages. After 2014 however hubpages stopped allowing affiliate links from users on their articles. So current testing observations are based on my own websites data. Here are some of my observation on which program is better.
Amazon, has better conversion rate. The brand name, return policy, refunds all in favor of buyers. Most of the products listed in the affiliate dashboard convert well. Also the dashboard also shows you which products you should promote for better conversion. The base percentage for amazon starts with 4%. And once you cross 30 or more sales, it raises to 6% and once you cross 200 products, it goes upto 8%. If you give more than 1000-5000 clicks to the amazon per day with decent conversion rate, you'd have a lot of good earning. Payout will be given to the bank directly using NEFT system. You can also get the cheque in the mail if you have selected that payout method.
FlipkartBefore you even use the links, it's better to get your bank account linked and website verified. Because unless you do this, the new system will not recognize your conversion and clicks. The base rate for each product varies in Flipkart. So for some product your conversion will start from 8% to 10%. Some product rates also fluctuate too so it all depends on the changing conversion rate offers offered by flipkart. There are also lot of good offers on mobile traffic as flipkart is forcing mobile conversion from offers. In case of payout, you can either redeem as voucher or bank transfer. This is second best program after the Amazon.
Ebay One of the hardest program to get into for affiliate marketers. Unless you are affiliated with say Hubpages or other similar site the conversion is also hard. It requires you to install one javascript file on your websites pages or CMS. And they track the traffic before approval. The conversion rates are CPM and CPC based. So you get paid some good amount of money from the conversion that happens. A lot of websites such as hubpages are making some decent money from this program. For solo bloggers it'd be harder to make money if they don't have 1 million views per day, which is easy for hubpages or ehow. This program should be last resort to apply because other e-commerce sites are much better in terms of conversion.
If you want to diversify the results then you have some of these options such as - infibeam, snapdeal, shopclues etc. In terms of revenue generation, infibeam is one of the lowest earner. Snapdeal does get some conversion during the sales and product launches. The rate is also good for the snapdeal links and banner ads. Shopclues on the other hand has yet to establish itself. So there is a lot of things to be done for the bloggers to push this brand at first place.
Do note that you need to send a lot of traffic in order to make some serious revenue from those sites. Also if you are solo blogger, tone of your writing has to be super humble and friendly for people to click on the link given in the article. If you try to be too pushy or too authoritative, or shady in the tone, then your conversion rate will fall in case of promoting these affiliate programs.