Optimus, Rodimus, Megs, Starscream, Soundwave, The Dinobots, Ironhide, Bumblebee, Astrotrain, Cyclonus, Scourge, Galvatron (Frank Welker) and any others that I remember are G1 because I can remember the more iconic voices.

Unfortunately there are a ton I can't remember like Prowl, Sideswipe, Sunstreaker, Season 2 Seekers. If I could recall them they would be G1 but my mind keeps making generic Transformer voices.

Ratchet is cranky old TFA Ratchet.

Arcee is a psycho version of Prime Arcee, I don't think G1 Arcee fits the IDW character at all.

Sentinel Prime is Leonard Nimoy.

Then there are the guys that have never had voices like Metal Hawk and Circuit that I normally end up with a unique voice in my head.

Now that I think about it, maybe I'm going a bit far when reading the comics and should get some help.