AUTOBOTS: Wedge
Why its not Ultra Magnus: I highly doubt even Optimus wouldn't have been able to completely deal with Hot Rod and Kup buying the farm while he himself was being hunted down by Galvatron's Armada. He also stood up to Galvatron, Cyclonus, Scourge and the Sweeps by himself to try and open the Matrix to save everyone, essentially sacraficing himself for everyone else. Plus he was a great field general and was put in a bad situation after Optimus was killed.
I agree with this.
Why it's not Rodimus: Everyone loves to slag on Rodimus for making mistakes, for his lack of confidence, or for whatever reason. Yet they don't realise 1 key point: We never got to see Optimus' early days/weeks/years on the job, past like 60 seconds after he became Optimus Prime. Did Hot Rod make mistakes? Sure, but so did Orion Pax. Did Rodimus have self confidence issues? Sure he did, but not only could Optimus have had them and we just never saw them, but Rodimus took over after having Prime running the show for millions of years on Cybertron & decades on Earth.
Nobody really ever gave Rodimus a chance. They mostly all went into "Screw this, WE WANT OPTIMUS BACK!!!" mode right from the start.
DECEPTICONS: G1 Megatron
1. The moron constantly chose to disregard his former scientist Second-In-Command whenever Starscream gave him advice. Whether it was about Megs' weapon of the week being faulty as Megs planned it, down to "Hey, there's something funny about your Stunticons" and it turns out that the robots Megatron happily allowed to walk into their basecamp were Autobots in disguise. Megatron never listened to the guy smarter than he was, and it always bit him on the butt in the end.
2. What really was his goal? Was it getting energy for the Decepticons to conquer, or was it kiling the Autobots? Because if killing Autobots had any importance to him, then why did he not allow Starscream to kill Gears in 'Changing Gears' once he got the personality circuit he needed? And not letting Starscream eliminate one of the enemy when A)the enemy would've gladly walked up to you and put your gun to his own head and B)it would be one less functional Autobot to hinder Megatron's plans.
And if Megatron's goal was to gather energy for conquest, then shouldn't he have focused more upon that goal over the weapons of the week that only served to attempt to kill Optimus, and yet always failed(see point 1)?
3)The simple fact that he allowed Starscream to live. If the first words we ever hear out of Starscream's mouth basically are "Megatron, you're a failure & an idiot, and we've never won due to you.", and then when you're revived on an energy rich world with no Autobots around to stop you & no Earthly power able to hinder you, why would you actually revive someone who wants to stab you in the back & take your job? Why continue to let him live afterwords when he tried to usurp Megatron?
And why, when your transformation mode requires someone to wield you for you to be useful, why on Earth would you 80% of the time land in the hands of the guy who wants to kill & replace you?!? What, was Skywarp or Thrust to busy to get another gun to shoot with?
Why it isn't G1 Galvatron: Yeah, Galvy was batshit insane, and yeah he'd sooner shoot his own troops than the enemy, but that is the key point: He'd actually shoot his own troops if he felt they threatened his powerbase(or if they told him water was wet & the sky was blue).
Why it isn't Ratbat: At least Ratbat seemed focused on his goals & actually got fuel for his troops.