Gen1 Megatron?
I noticed that my MP Megatron's feet have 'decayed' as reports originally mentioned, and I don't think there is anything that can be done about them (because it isn't metal, or regular vaccumised plating).
As for Gen1 Megatron, I think maybe a metal polish you can get in stores would work, but you would probably need to remove the feet from the (plastic) toy, and clean them throroughly after polishing them (to remove any chemical residue), before putting them back with the rest of the toy.