This is a toughie...
Helix fossil (Omanyte-Omastar)
I love these squidish snail! Its tenacles and spiked shell make it hard to resist, oh wait, but those eyes and mouth sure don't! Still, I really enjoy this Pokemon. 7/10
Dome fossil (Kabuto-Kabutops)
This guy has always taken the back seat to Scyther for me. Sure, it has nice slicers, but it's a bit redundant and lackluster. 5/10
Root fossil (Lileep-Cradily)
At first, I didn't like this Pokemon at all. But once I really look at its design, I realized the yellow on its head were designs, and the eyes were the yellow beneath its forehead. Overall, one interesting and sorta cute Pokemon. Agree with poster above! 8/10
Claw fossil (Anorith-Armaldo)
I had the same issue with this pokemon from the ruby sprite. I thought the eyes were the red designs on its forehead. Beyond that I am not sure whether to admire its use of metal to form the exoskeleton and brilliant wings or be underwhelmed by those wide-set eyes. I like him. 6/10
Skull fossil (Cranidos-Rampardos)
This one is tough for me. I have always wanted to see a dome-headed pokemon, but rampardos leaves me with a bland aftertaste. I like the two large horns that form a V, but I am not found of the small red eyes with not white or shine, the color palette, or the lackluster design. 4/10
Armor fossil (Shieldon-Bastiodon)
I love this pokemon. A culmination of a triceratop and a bulldozer. Though its concept is ambitious, the design still has an ease to it. This was my first fossil pokemon I selected my first run through a game. The others lack either uniqueness or aesthetic to be a first draft pick. 10/10
Plume fossil (Archen-Archeops)
I genuinely like this pokemon a lot. The concept of the first bird species is great; taking the pterodactyl to a more interesting place; plus the color scheme is perfect. Though, it does have one major flaw - that face. Why couldn't he have either an elegant or intense set of eyes, rather than derpy. 7/10
Cover fossil (Tirtuoga-Carracosta)
I actually love tirtuoga! And, these turtles have nice sharp beak-like mouths, which I love. But....Carracosta is bulky, dull, and far from aesthetically pleasing. 5/10
Old Amber (Aerodactyl)
I don't have any issues with Aerodactyl. I just think I would appreciate this one more, if there was a pre-evo. I really don't like when a pokemon, especially a full-grown one, doesn't have evolve from a weaker species. And, this one seems a bit generic, and not overly enticing. Though, I do not dislike this one. 6/10
Ranking:
1.Bastiodon
2.Cradilly
3.Archaeops
4.Omastar
5.Armaldo
6.Aerodactyl
7.Carracosta
8.Kabutops
9.Rampardos