Iconic doesn't mean good. Not a single one of them has truly what it takes to be considered a Kamige. Granted, S;G is preety close, but still falls flat.
That said, as Clephas mentioned above - for one to be a kamige does not necesarilly mean it has to be super entertaining. That goes the other way around, as well - a vn does not have to be a kamige to be truly entertaining. In the end, "kamige" is just a tag, people tend to stick to games they feel to have something more than just being plain entertainment carriers. Some games even do have artistic value. Does that mean they will be trully great as games, though? Not necesarilly. Beyond being able to distinguish between those factors, one can't forget that the most important thing is it's own, personal enjoyment that comes from reading these games and other people's guides shouldn't ever cloud your own judgement.