1 - Masterpiece Optimus Prime 2 - G1 Optimus Prime 3 - R.I.D. Optimus Prime 4 - G2 Optimus Prime 5 - Beast Wars Optimus Primal Honourable mention - Hybrid Optimus Prime
In terms of the toys. Masterpiece is the greatest no doubt. But: Cybertron/Galaxy Force Prime RID Prime Those are the two main line Primes on the top of my list.
Bendy Prime. It took the Laser Prime transformation, and actually made a good looking robot out of it. Cyb Prime kicks ass, too. Despite the futuristis artillery piece look of the alt mode, it's still looks good, and the bot mode os pretty decent too. It's only drawback is that it has a super mode. I like my Robot Masters Prime, too. But, it's been pretty heavily kitbashed, and I'm still not finished with it. I'm pretty confident that Classics Op will be my Favorite, once I have one.
In terms of mold, I love the Generation 2 Laser Prime. The only thing that disappoints me is that horrid color paint job and whack decals. After that I'm not really sure, though I do think that Cybertron Prime is pretty damn cool (even though I don't own one). If he counts, I think that Superlink Rodimus Convoy has a great design to him.
MP Convoy, though he's still Optimus Prime to me. I like them all though, everything from Orion Pax to Galaxy Force. Within my collection is the Optimus Prime collection.
I'm also going to have to go with Masterpiece Prime. Its Prime the way he should be. I do still like most of the other Prime toys though,but if it came to picking one thats the way I would go.
As for Primes currently in my collection 20th/MP Prime. From a nostalgia point of view G1 Prime. I wish I still had my G1 Prime with arm crazy glued on and missing peices too. That one still makes me remember waking up Christmas morning and being so happy "Santa" brought me one. I hope Hasbro does Re-reissue that mold as has been rumored.
20th Prime, just because he looks like someone took the cartoon model of G1 Prime and made it "realistic". and since I added repro-stacks to mine he looks that much cooler.
20th Anniversary, hands down. Second place would be the original. Mostly because he was the second TF I ever owned. I'll let you guess who was first.
1. G1 original. The perfect toy, was like 3 in 1. You have the trailer, you have Roller, you have Prime itself. 2. Hybrid. I like it because even though it is scaled small, it has ridiculous detail. 3. Powermaster Prime. Upgunned, up-armored and out for a killin'. I guess you could amend it to include the Nucleon Quest black Prime too in this.
1. Black Big Convoy 2. Universe Nemesis Prime 3. Big Convoy 4. Black "Battle" Convoy (Car Robots) 5. Vector Prime (GF Version only) 6. Galaxy Convoy 7. Armada Bendy Nemesis Prime 8. God Fire Convoy 9. Rebirth Convoy 10. Galaxy Force Vector Prime (repaint) 20th Prime, despite all it's coolness is not on the list. While he's a great figure, he's too unstable (his feet pop off at the drop of a hat), big, and bulky. Outside of a display shelf, he's not that much as a "group" figure, which is what I prefer.