Not your favorite. Not the ones that geeks in their parents' basement yell the loudest about (because no one gives two shits about Erector). Who do you think are the ones that people remember years later, who they love the most?
Here's my stab at it:
1) Optimus Prime
10) Omega Supreme
My thinking is this: Optimus and Bumblebee are given. Soundwave seems to be the Decepticon who comes to mind first for most people, followed by Starscream. Everyone remembers Devastator; they probably can't tell you the name of a single Constructicon or other gestalt. Jazz has the most personality of any Autobot (who are mostly interchangeable if you get rid of their looks and special abilities). Laserbeak narrowly beats Rumble, since most people seem to think a bird with laser guns is cooler than a guy with piledriver arms. Grimlock seems to be the only Dinobot who people remember. Omega Supreme, despite a mediocre toy, was the first "city" Autobot and stands out.
Honorable mentions go to Megatron (who, really, most people just recall as "the bad guy who orders Soundwave and Starscream around and who Starscream shoots at") and Wheeljack, who really seems to be the only other early Autobot with much personality on the show, as well as one of the better toys.
I'll also wager these would be the bottom three--not referring to toys and characters people didn't care about, but those they actively hated:
3) Galvatron: Most folks see him as a shitty Megatron replacement.
2) Wheelie: He really fucking grates on most people I know. Even Simon Furman has gone on record talking about how much he loathes Wheelie.
1) Hot Rod/Rodimus Prime: No matter how cool they make him in later incarnations, he's always got the same problem as Galvatron: he's seen as a shitty Optimus Prime replacement. Plus kids actively blamed him for Prime's death because of his intervention in his final battle.
Yeah, this is a weird question for this site, but the post about Grimlock in the video games forum made me think about this.