Saul was comic relief for the most part, do we really need a 5 season melodramatic series on him?
Yes
As for Mike, the mystery around his nature is what made him interesting. Let fans come up with their own ideas as to how he became like he did, rather than try and complete every little piece of the Breaking Bad jigsaw puzzle.
Couldn't disagree more with this part. The season 1 ep about him getting revenge on the bent cops who killed his son was one of the series' best eps for mine and gave you a new slant on his relationship with Jessie in BB, masterful stuff.