These are not in any order, but I felt "best" and "worst" weren't exactly the best way to describe each kings.
Weak Kings - A weak king is one who is either incredibly ineffectual or doesn't rule his kingdom.
+Aenys I Targaryen - The very first weak king of the Seven Kingdoms. Rebellions sparked not long after he became ruler. Was ineffective at stopping them as well. Had to rely on his younger brother Maegor.
+Viserys I Targaryen - It was a toss up between putting him here or down below under Neutral Kings. His reign was very... plain. Nothing really happened. I placed him under weak kings though because of the succession crisis that followed his death.
+Baelor I Targaryen (the Blessed) - Of the 2-3 Targaryens that caused that stupid saying "When a Targaryen is born a coin is flipped" to be assumed for all of them even though 99% of them were actually sane, and the few that do get counted as mad had very good reasons for their mental breakdowns... Only he and maybe 1-2 others could conceivably bonifide be called mad from the get-go. Anyways he was a weak ruler.
+Aegon V Targaryen (the Unlikely) - I am putting the entirety of Robert's Rebellion as his fault. He was a weak ruler and couldn't say no to his children. Nevermind the whole burning of Summerhall and the killing of most of the remaining Targaryens...
+Joffrey I Baratheon - Weak and incredibly stupid. Not to mention he is a tyrant (mentioned later)
+Tommen I Baratheon - Tommen is an incredibly weak king so far, but he has the chances of being a good king (as in nothing happens). His success as a ruler depends entirely on his advisors. If he has strong advisors like say.. Kevan Lannister and Maester Pycelle, he will be an okay king. With advisors like Cersei, he will be a terrible king.
Strongest Kings - The most effective, and strongest rulers. While peace may not always have lasted, and they may have died in battle... They would be the rulers that went above and beyond.
+Aegon I Targaryen (the Conqueror) - He forged the kingdom in war. Clearly the greatest warrior king of the Seven Kingdoms. Not only that but he was able to juggle all of those powers and ensure it survived out of it's infancy. Even with the weak and stupid Aenys that followed, and the tyrant Maegor. His kingdom did survive past him so he did his job right.
+Jaehaerys I Targaryen (the Wise) - It is extremely hard to decide who is a better king between Jaehaerys and Aegon. That is one of the reasons this list is not numbered.
+Daeron I Targaryen (the Young Dragon) - The conquest of Dorne did not last that long, but it was a great and first step in years to expand the kingdom. It also led to the eventual absorption of Dorne under future rulers. While his reign wasn't really nearly long enough to make him a truly great king, I couldn't in good faith put him anywhere else on the lists..
+Daeron II Targaryen (the Good) - Belongs on this list as he was king during the Blackfyre Rebellions, which I would place more on the stupidity of his fathers actions then his. While definitely not the strongest of kings, he did manage to bring the kingdom back together after rebellion and ensure it stayed whole.
Tyrannical Kings - A Tyrannical king is one who goes about squashing the rights of the lesser people/lords.
+Maegor I Targaryen (the Cruel) - The first of the Tyrants for the Seven Kingdoms. Westeros version of Henry VIII. Honestly except for his strive to have a son, he wasn't exactly a terrible king. After having such a weak king precede him, the throne needed Maegor's iron fist. Without Maegor, Jaehaerys would not have been as effective a ruler.
+Aegon IV Targaryen (the Unworthy) - Aegon IV I couldn't place anywhere else. He wasn't a weak ruler, he wasn't a strong ruler. He couldn't keep it in his pants though and his deathbed legitimizing all of his bastards led the kingdom to war later on.
+Aerys II Targaryen (the Mad King) - Aerys the Mad is a very troubled figure. When he was younger, he was actually a very great king. But being captured by the whole Duskendale Defiance and in prison all that time broke his mind and turned him into a tyrant. He definitely wasn't a weak king, and during the beginning of his reign he was strong.
+Robert I Baratheon (the Usurper) - Elia Martell, Rhaenyra Targaryen, Pisswater Prince. He may not have done the raping murdering himself to secure his rule, but he also didn't punish them. I cannot place him under weak kings, nor can I place him under strong kings. Some of his actions were very tyrannical though.
+Joffrey I Baratheon - The only ruler that gets a second mention. The only thing that kept Joffrey from being a Tyrant was that he was an incredibly weak ruler
Neutral Kings - These Rulers are ones who didn't exactly stand out in one way or another. They weren't weak rulers, they weren't strong rulers. They were just... rulers.
+Aegon II Targaryen/Rhaenyra I Targaryen - Including them both together, because Rhaenyra held Kings Landing and basically ruled the kingdom for a few months. Seriously neither of them reigned long enough and they spent most their reigns in war against each other. They weren't very weak because they were able to draw large groups together nor were either very strong because they were unable to secure the throne without war. They both had slight leanings towards being tyrants.
+Aegon III Targaryen (Dragonbane) - Aegon III was basically what, the last Targaryen standing? He really didn't stand out as a ruler. I mean he kept the peace but that's about it yeah?
+Viserys II Targaryen - While Viserys was a very effective ruler as he was hand of the king. He wasn't exactly strongest ruler material.
+Aerys I Targaryen - He doesn't really fit anywhere else on the list.
+Maekar I Targaryen - He doesn't really fit anywhere else on the list.
+Jaehaerys II Targaryen - He doesn't really fit anywhere else on the list.