Good fecking grief, children. If you're going to have a list, explain why you rank things the way you do. Otherwise it's not discussion. Just spam. And that is never a good thing.
Anyhow. Let's see.
1 - Kabutops. The anthropomorphic, arm-bladed horseshoe-Crab-Trilobite-Whatever-beast gets my first place on grounds of design alone. I've appreciated the thing from day one - even in the days where its physical-attack geared nature and lacking movepool in the terms of physical attacks made it not particularly viable. I don't use Kabutops often, as there are quite a few better alternatives to it, but the thing is frelling nifty looking and MOST of the fossils have viable alternatives. So Kabutops it is! (Also, Kabuto is adorable)
2 - Aerodactyl. Not much to say about Dactyl, really. It's not actually a good representation of a Pterosaur - more of a strange prehistoric wyvern from hell with an underbite. But it's fast, it hits fairly hard and it carries a fair bit of diversity. The fact it was a 'bonus' fossil not part of one of the usual 'pick one' dealies also helped.
3 - Carracosta. Frankly, I'm not sure why the Archelon gets no love. It's the awesome sea turtle that Blastoise wishes it could have been, but with 50% more rocks and 50% less ridiculous cannons and cow face. Besides, after Cynthia repeatedly dashed her 10-levels-higher Braviary into one of mine in White and it only sort of MILDLY got dented, my levels of respect for the beast rose significantly. Also death flippers.
4 - Archeops. I was torn about the placement here. I like Carracosta and Archeops about equally and there is a certain sense of sheer hilariousness to Archeops due to the absolutely ridiculous way it flail-flies and its mismatched color-scheme. At least in terms of official art, Archeops looks like something that was made out of parts that don't quite fit - but fan art can (and has!) make the thing look pretty snazzy. Unfortunately, the poor thing is crippled by its absolutely retarded ability - and while that can be shuffled away in doubles or triples (and a close friend of mine has made a lovely zombie apocalypse vector out of it by pairing it up with Cofagrigus) - it otherwise... Yeah. Still gets a pretty high place because I do enjoy the weird quasi-dinosaurian-quasi-archaeopteryx.
5 - Armaldo. Alright. First off, let me begin with a fact - Anorith is beyond adorable, which is kind of hilarious when you think of the fact it's based on a fairly massive apex predator and is actually very true to the creature it was based on. Armaldo loses some points for sort of acquiring a somewhat nonsensical and very generic kaiju sort of conformation and losing the adorable wing-mirror sort of eyes for angry animu gecko eyes - but I am still quite fond of its large plated meta-arthropod nature and its type combination is rather fun really. I like my bug-types, damnit.
6 - Cradily. I also very much like my Grass-types! Cradily's official art makes it look a bit derpy but it has vast amount of utility hidden in that stalked green mass of its and with the right movesets it is an absolute force to be reckoned with. Of course there is the matter of Crinoids not being plants (they are echinoderms, more closely related to starfish, brittle stars, sea urchins and sea cucumbers) - but neither are fungi and yet assorted mushroom Pokémon are Grass-types. We'll give them a pass.
7 - Tyrantrum. This one I am vaguely torn about. I get what they were going for with the Tyrannosaurus rex / stereotypical king sort of look and the craggy sort of scales and I very much appreciate the fact they gave it feathers (albeit only partially) - but I feel the execution, at least officially, leaves a hell of a lot to be desired. That name too. Not exactly awe inspiring. Ah well, I guess we needed a T. rex that isn't actually Godzilla.
8 - Omastar. Omanyte is fecking adorable, but Omastar always looked incredibly stupid to me with its derpy eyes and its four-way beak and its general "What the fuck AM I even" surrounding it. They got too unwieldy to live and died out only to be brought back to life because what has science wrought. I'm sure there's probably some way to salvage the thing (I feel I may have done so once in the past?), but with all due respect to "Lord Helix" or whatever kids these days call the thing... Its only saving grace is being an ancient dead cephalopod.
9 - Rampardos. Ahh, Rampardos. The first 'proper' dinosaur fossil we got and it was fairly surprising they went with a pachycephalosaurid - but between its singular rock type, its stats (pure attack and fuck-all else, which doesn't allow it much in term of utilizing that ridiculous attack stat) and its general appearance (a horrible case of Sugimoritis indeed) leaves the thing occupying a fairly low spot on my list compared to the rest of the fossils. I don't hate it really, but I don't like it all that much either. Leaving this one to Roark.
10 - Aurorus. This creature has only one purpose - and that's to breed on its signature move, Freeze-Dry, into far-superior Pokémon that can use it far better than it ever could. That and to give Gamefreak a chance to play with a texture gradient whatever engine. This thing would be my least favorite of the fossils, if not for one last thing...
11 - Bastiodon. Or should I say Bastardon, as the thing is an absolute fucking bastardization of the entire suborder Ceratopsia. With a face that only Byron could love (and true to form, HE LOVES BASTIODON, AND HE LOVES DEFENSE!!! *backgroundsplosion*) and basically being a heap of defense and fuck all else, Bastiodon seems to serve one purpose and one alone - to be incredibly, incredibly annoying. Bad show.