I could name a hundred songs off-hand that I love for one reason or another. For that reason alone I think they are good songs. Why do I think they are good songs? Because I love them.

I know the reasoning is circular. No one has yet established a universal criteria for good. We cannot assume that because a song sells lots it's necessarily good. Or because it sells little it's necessarily bad.

Some of what are to me great songs, and may receive derision from other people who have different taste or likes/dislikes in music:

Boys of Summer
Surfin' Safari
Maggie
Roddy McCorley
Hard Rain's a Gonna Fall
Stuck Inside of Mobile
Fool Like Me
Summer of '69
Amazing Grace (by the Royal Scots Dragoon Guards)

I doubt more than two or three people anywhere would agree with that partial list. I like 'em because I think they're good, and I think they're good because I like 'em.