Unfortunately if you view Transformers through modern eyes like I do everything from G1 looks terrible and like they are the worst Transformers ever made.

I kinda wish I could forget modern Transformers temporarily so I could enjoy the toys from my childhood. They are the part of my collection I keep more as a "look where it all started" thing rather than something I enjoy.

I skipped all of Beast Machines and I only have three Armada toys and a single Energon toy so I don't have those figures that are generally considered terrible from the modern era.

Worst modern era toys I have are Voyager Double Dealer as I just think that mould is pretty bad. Also the fragile MP figures like MP-3, MP-5, MP-9 and MP-36 as I can't actually play with them so it takes 99% of the fun out of them. Those are the ones "in my collection" I hate. There are some stinkers in the movie and CHUG lines also that I have, but I don't consider them as part of my collection as I want to sell them and they are packed away.

As for the best stuff, well I have plenty. HasTak have made far more great toys over the years than bad stuff.

-I feel like MP-13 Soundwave is still the best MP, even though he only comes with Laserbeak unlike the Hasbro version. He was the first MP where I went "it's like he's right out of the cartoon".
-The MP Inferno/Grappel mould is amazing.
-Magnus is probably the best looking MP of them all with his size and cartoon accuracy.
-All of the G1 based Unite Warriors combiners are amazing to have.
-The Classics, or in my case Henkei Seeker mould still is the best mould of all time IMO. It's simple, fun and comes from a time before the current round of cost cutting made Transformers what they are today.
-I feel the best triple changers we've gotten are the LG Blitzwing and Octane.