Best Brand of Omega 3 Fish Oil Supplement?

Planning to buy an omega 3 fish oil supplements for my Dad this upcoming July. But when I've search it a while ago, i just surprise that there's a lot of brands of this kind of supplement. I want to know if what's the best Brand of Omega 3 Fish Oil Supplement nowadays? it's okay to me if it's quite expensive as long it delivers good result on my Dad's health. Some of the brands I've browse a while ago are Maxalife, Puritan and Nordic Naturals. I will wait for your reply guys. All will be noted.