Well, damn. It looks like the Transformers Hall of Fame has put both of my all-time favourite Transformers on their nominee list: BW Megatron and (technically) Rodimus Prime. Both are on my list of top fictional characters, both are important to my fandom nostalgia. When it comes right down to it, could I really decide?
Eh, actually, if you like over-thinking this sort of thing (and you know I do) the choice is easy. BW Megatron is far more the type that deserves to be in any kind of "Hall of Fame", and for many reasons. He's not only popular, but seems to have had an impact on the franchise, as it has since produced more sophisticated bad-guy leaders that could, in theory, have been cast in his mould. Rodimus Prime, in contrast, is virtually forgotten, as there is a Hot Rod role, but no place for a leader who isn't Optimus Prime, and no real change to Transformers archetypes that could potentially have stemmed from him.
Secondly, Beast Wars Megatron was a better-written character than Rodimus in any form. While Rodimus Prime was likeable, and he was a great idea for a character, he never really had any consistent character arc. He had his issues with insecurity wrapped up in one episode, only for them to reappear again and be wrapped up again, while other episodes he was totally in control. He didn't go through a period of insecurity and then get over it as part of the plot, it just appeared and reappeared without warning. It's not the fault of the character, but rather that the writers never gave enough of a damn to plot out a real arc for him. I like Rodimus because he can be heart-bustingly insecure and wonderfully sarcastic, but he was off and on with all this, rather than building towards a permanent change.
BW Megatron, on the other hand, became more unhinged as the story went on, his plans ever more grandiose, until he seemed to have gone bugfuck. Some of this depended on retcons, but nonetheless, Megs travelled a straighter and more focused path than Rodimus Prime did. I also love Beast Wars Megatron's personality, but in that area, he's equal with Rodimus, though they appeal for different reasons. BW Megatron is, in short, cut from a better quality of cloth.
And yes, I realize that in theory the "Rodimus" initiation represents all other versions of the character, too, versions that I know nothing about or don't much care for, but since Rodimus Prime is the Peculiar Olympian here, he's what gets discussed.
On a personal level, I also consider the issue of seniority: Beast Wars was my first Transformer show and my gateway drug into fandom, so BW Megs has that cachet. Furthermore, while both shows are not great, BW holds up better (see "better-written character") than the original cartoon (all seasons). All in all, despite the debacle that was Beast Machines Megatron, BW Megatron still would be more deserving of recognition. He's probably going to win this poll, and nothing would be more appropriate.
However, I'm going to randomly put in some Rodimus votes here and there, because he's still one of my homeboys.
They're also adding Arcee into the Hall of Fame, almost certainly because the original Arcee (again, all versions are lumped together, including the modern one that sprang from Simon Furman's horrible head) was the first long-term prominent female Transformers character. So yeah, that's a legit reason, though I wish G1 Arcee had a more developed personality to go along with that. She was always just kind of…there. Sometimes the "warrior", sometimes the damsel in distress, never building up to a whole picture of a character.
Blackarachnia was also nominated this year but never made the final cut, which is a shame. I had my issues with her character arc in certain spots, but it was nice to see a Transformers character who actually had some character development. I didn't expect that to end in a final-cut nomination, though, since "had character development" isn't usually what people who run these things are looking for, and besides that "Blackarachnia" hasn't really become a Transformers name-as-institution like Arcee. Still, she was cool.