Just copying and pasting my opinions on Bionicle from the Original Unpopular Opinions Topic to here. Plus adding a little more.
I like the Bohrok-Kal and Vahki a lot (and feel that they're under appreciated)
I really liked Krekka a lot when I was younger, and I still do. I really want to get him.
I feel that 2005 was an important year (more specifically to the character development of the Toa Metru/Hordika)
Keeetongu might be my favourite Titan of that year.
I thought the (rubber?) Maks in 2006 looked really cool and unique.
I didn't mind most if not all the changes made to the Toa Mahri.
I didn't mind the "changes" made to the Toa Nuva in 2008 and I like them because I feel that they fit the aerial/swamp aesthetic very well
I like Solek, and he's my favourite of the AV-Matoran. This doesn't include the Shadow Matoran. (Radiak is my favourite of them all.)
I like 2009, and I feel the overall design and setting harbours more to the original concepts, ideas and setting of Bionicle than the later year of Bionicle until 2009
There's no set in 2010 that I didn't like
I like the idea of the revival system of th Red Star, and has some sense to it. (I'll explain why later)
The 2015 sets have the same, and if not more (thanks to the Gearbox) complexity that G1 sets had (outside of the "Titan sets" introduced that year)
I really like the Skull Villains (Including the LoSS) because of their uniqueness, and I feel is inspired by the Rahi sets (I'll explain later)
The 2016 sets I feel have more complexity in their (torso) design more than any previous G1 set (this is specifically to the Creatures, Pohatu, Lewa and Gali. The rest don't count because of their status as "Titan" sets (correct me if I'm wrong), being $20)
I think Umarak the Hunters lower leg design looks fine to me.
Pohatu might be my favourite of the medium sets, and I might like his Unity form with Ketar more than most of the others.
Ketar is literally a reverse of Akida. Ketar looks odd (to some), but has (odd to some) play value and functionality for itself, while Akida looks good (probably my favourite Creature), but literally has no functionality on its own (the upper body thing more or less applies to the Union with Gali.)
The Beasts all awesome, and Quake Beast may be my favourite.
I don't mind the amount of trans blue on Ekimu the Mask Maker.
I may do it and HF later.