Well, I haven't seen the Jem cartoon but I have seen the dolls, and I admit I usually like the Misfits better in doll form! I decided a while ago that I wanted to own a Jem doll and ended up choosing Clash (purple hair!). I don't think she's in the cartoon much but she's an awesome doll.
Clash is only a Misfit in her own dreams >.>It's ironic because I'm a Misfit person through and through but the prettiest doll to me is 2nd edition Shana. She is everything I wanted in a fashion doll as a kid, but never had the opportunity to get till I was a fresher at university

I agree on the QC thing. There are two brushable collections for G4 that I really like, and I get the members of each mixed up, but one is the one with Dewdrop Dazzle in.
Also!
This is a sort of personal thing for me with G4, but they also associate to me with travel. My first several G4 ponies came from places I visited.
So my first three came from Porvoo, Finland (Applejack, Rarity, Lily Blossom).
I picked up some in Lille (Starswirl, Rarity and the Carriage, Dewdrop Dazzle & Pinkie Pie. Those came as combined sets otherwise I wouldn't have got Pinkie xD)
Cadance with the fancy wings I bought from the main station in Prague.
Starlight Glimmer with the bow headband came back with me from Vienna.
And Water Cutie Blossomforth came back with me from Portugal...she was was the only G4 pony in the entire hypermarket in Lisbon.
Some of these I also have photos of in their respective locations.
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Oh yes, and a couple of more recent ones came back from Tel Aviv airport...I had a conference in Jerusalem where I was presenting to help a friend out, and on the way back I found some of the ones I hadn't found in the UK. One is one of the water cuties with wings. Lily Blossom I think. Also I think Tempest Shadow? I forget now.
Closer to home, Feather May and Honeybuzz came from Harrods as a moving in present to myself when I started my MA in London in 2011. I never saw that set in stores again. If I'd known I'd never see them again, I'd have bought more of the set - I am still missing a couple ><. That's the other favourite brushable set of mine

And of course there's Fluttsi, who my sister bought for me here but who travelled all over Japan with me during my fieldwork. I even have a photo of her looking out at the ice across the north of Russia on the plane home! She also came with me to the course/conference in Lisbon and to my first ever conference in York.
FLuttsi on location...
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So, while FIM and the brony toxic drove me away from G4 and away from the overall pony fandom for a spell, they also kind of represent travelling and adventure to me.
I have some that came to live with me from other places as well. My Cupcake came from Scandinavia, I think Sweden, and I have a feeling one of the others did too. I know Ploomette and a couple of others came from France and Snowcatcher and Diamond Rose came from the US.
And there are some that I picked up in the charity shops and car boot sale where I lived the last year in London and where I miss living SO MUCH at the moment, that it's nice to have a little piece of that place here with me now too. I also have one which I bought at the big TRU in Brent Cross before it shut down, as a "farewell TRU" pony.
So overall, and especially at this time when travel is not possible, it's nice to see my G4 ponies and remember all the places they came from or went to or both

That's maybe not what the OP was looking for when asking the question, but it's the reason I have affection for G4 ponies even when I hate the brony culture and am not big on FIM, friendship-brainwashing and the mane 6 xD.