I thought
JetSkyJetfire was the perfect choice to launch Commander class. He's big, he's bulky, and there was a demand for a toy that wholey committed to the animation look. I admit I always preferred my Jetfires Valkyrie flavoured, but I'm not gonna deny the obvious here. There was certainly a demand. And Hasbro delivered.
Sky Lynx is less obvious. I would 100% disagree with the idea that Jetfire is niche, but Sky Lynx certainly is.
@Andrusi is right though. The character's alt modes were perfect for Earthrise (much like how Jetfire's Skyfire-accurate look was perfect for Siege) and the end result was a beautiful toy that did everything it had to do wonderfully.
Kingdom Rodimus is a very weird entry for a variety of reasons, so I won't touch on that but coming back around...
Bulkhead. I'd debate that Bulkhead has had more impact than Jetfire. Sky Lynx? Yeah I'll give the Bulkhead crowd Sky Lynx, but not Jetfire.
This is very anecdotal (then again so is the notion that Bulkhead had more impact) but...
To me Skyfire (and therefore Jetfire) was one of the things that made Transformers special to me.
Fire in the Sky not only gave us a backstory for Starscream that hinted at a world larger than the scope of the show, it not only gave us our first Decepticon-turned-Autobot, but it also gave us our first Autobot jet/flier at a point in the series where that seemed like something that just wasn't possible.
So hints at a broader backstory and world, first faction changer, first Autobot to have an aerial alt mode. Pretty big stuff. To little kid me anyway.
Then as I got older and looked into it I figured out his toy was this really cool looking Japanese mecha thing, not like anything else I'd seen from G1 Transformers before. It added to the mystique. As did learning about the legal stuff around him. Why they had to change his design. Why TT would never reissue him, etc...
Toss in his name being used for a prominent character in the UT and his role in RotF and I think you can certainly argue that "Jetfire" as a character has currency as a Transformers character that goes a long way for anyone who remembers the original show with any fondness.
