There are so many affiliate sites but all have their own pros and cons. Other thing is how you feel about each network. Because when you go though their deal you know you can promote those or not. Even that's not enough. You might feel you can promote but then you need to see if it really work for you or not. Only way to find out that is testing these offers. Some need paid traffic and you have to see if you are up for those.
Amazon - in-house affiliate program low commissions but good for starters. You don't need paid traffic
Peerfly - They have lots of good pay per lead offers. If you can get in then you will find everything is great.
Maxbounty - Same like Peerfly but probably more a bigger offer list. You have to call them to activate your account
CJ - Lots of great products but probably can't earn unless you know how to use paid traffic.
ClickBank - High commissions but it's hard to promote these offers with free methods.
Can't say anything to say about other networks.