Some historians see each of the Severan emperors making positive contributions to his reign. Would you agree with them?

Some historians see each of the Severan emperors making positive contributions to his reign. Would you agree with them? [A topic like this would basically allow you to talk about the reign of each of the Severans (positively, negatively, or a bit of both) from Septimius Severus (ascended the throne in A.D. 193) through Alexander Severus (d. 235).]

Half a page answer is good :)