Having been on here so many times and with so many cards to keep track of when deckbuilding, I ended up making an excel database (out of frustration) to show which creature cards work best, given their mana/ability/p-t values, and factored in card ranking from here. Many many thanks to your inputs.

So yes, by far the best one drop result was THIS crazy beast. The sacrificial cost is entirely irrelevant.
At a whopping ~1150% value, followed by Mother of Runes at a distant 527%, it goes to show CMC cost for value is well recognised. Of course, increasing the {1} to {2} to factor in stifle, which results in half the original score, it is still higher than that Mother.

As for 3rd and 4th places, they were Delver of Secrets at 339%, and Vexing Devil at 325%

As for the others in their CMC tiers -
Best {2} drop: Qasali Pridemage @ 160%
Best {3} drop: True-Name Nemesis/autoc... (see all)