Okay, time to make a confession, something I use to see...
Skyfire and Jetfire aren't exactly the same character, in spite the name change because the copyright problems with Macross Valkiries, AKA Robotech.
Skyfire is from G1 cartoon, the gentle gigant, the pacifist scientist (the one that attacked Megatron without hesiation, yeah), the lost child that got enclosed in an icecap for millenia and when he woke up, everything was a madness. The one that the fandom only cares about because his relationship with Starscream, not because his sad story.
And it comes from just ONE episodie.
On the other hand, Jetfire is from the comics and every other continuity. He also is a scientist in mostly of continuities, but a pacifist?? Not at all! He's totally okay if he has to break some Dcon chasis in almost every incarnation. In Cyberverse, he's obssesed with beating Sky-Bite; in War for Cybertro- Siege, he killed Skywarp shooting him in the back. In Armada, he's am insufferable Autobot SIC and Optimus' pants... And, in mostly of those continuities his relationship with Starscream is just casual or just Zero.
Now, can you point which version is the most popular??
Yes, surely you can.
Because fanbase loves him only because they want him to be Starscream's bitch, not because they find him interesting or even nice.
.