Here's my opinion on my evolution on Power Rangers:
Mighty Morphin
Best of the series, that was until the second half of Season 2, when Rocky, Adam, Aisha and Kat came along
But luckily out of these four, Adam was the only one who grew on me.
Zeo
Great evolution to sequel MMPR, especially later on when they brought Jason back (even for a short time) to be the Gold Ranger.
Turbo
I didn't care for it, especially bringing Justin to be the Blue Ranger, it may have worked in Super Sentai with Dairanger and Ohranger, but it just didn't fit with the others. Then they bring in a new team, but still has quite a lot of kinks in there.
In Space
Best show since Season 1 and the first 1/2 of Season 2 of MMPR
Lost Galaxy
Wasn't average, but it did get better as it progressed, especially when Mike returned and became the Magna Defender and when Karone (formerly Astronema of PRIS) came back into the picture.
To be continued.........................